CN114257970B

CN114257970B - Method and apparatus for supporting user equipment to network relay communication in wireless communication system

Info

Publication number: CN114257970B
Application number: CN202111048457.6A
Authority: CN
Inventors: 潘立德
Original assignee: Asustek Computer Inc
Current assignee: Asustek Computer Inc
Priority date: 2020-09-21
Filing date: 2021-09-08
Publication date: 2023-05-30
Anticipated expiration: 2041-09-08
Also published as: ES2942038T3; KR102498723B1; US11259350B1; EP3972380A1; CN114257970A; US20220132605A1; KR20220039587A; EP3972380B1

Abstract

The embodiment of the application discloses a method and equipment for supporting user equipment to network relay communication in a wireless communication system from the perspective of second user equipment, wherein the method comprises the steps that the second user equipment initiates a first program for establishing one-to-one connection with first user equipment for unicast communication between the first user equipment and the second user equipment, and establishes one-to-one connection with the first user equipment for the second program for the user equipment to network communication between the first user equipment and a network node through the second user equipment; when the first procedure is initiated for the unicast communication, the second user device transmits a first PC5-S message to the first user device, the first PC5-S message containing quality of service information for the unicast communication; in case said second procedure is initiated for said user equipment to network communication, the second user equipment transmits a second PC5-S message to the first user equipment, the second PC5-S message not containing any quality of service information for the user equipment to network communication.

Description

Method and apparatus for supporting user equipment to network relay communication in wireless communication system

Cross Reference to Related Applications

The present application claims the benefit of U.S. provisional patent application No. 63/081,312, filed on 9/21/2020, the entire disclosure of which is incorporated herein by reference in its entirety.

Technical Field

The present disclosure relates generally to wireless communication networks and, more particularly, to methods and apparatus supporting UE-to-network relay communications in a wireless communication system.

Background

With the rapid increase in demand for large amounts of data to and from mobile communication devices, conventional mobile voice communication networks evolve into networks that communicate with Internet Protocol (IP) data packets. This IP packet communication may provide voice over IP, multimedia, multicast, and on-demand communication services to users of mobile communication devices.

An exemplary network structure is an evolved universal terrestrial radio access network (Evolved Universal Terrestrial Radio Access Network, E-UTRAN). The E-UTRAN system may provide high data throughput for implementing the above-described IP-bearing voice and multimedia services. Currently, the 3GPP standards organization is discussing new next generation (e.g., 5G) radio technologies. Thus, changes to the current body of the 3GPP standard are currently being submitted and considered to evolve and complete the 3GPP standard.

Disclosure of Invention

A method and apparatus to establish a one-to-one connection between a first User Equipment (UE) and a second UE is disclosed from the perspective of the second UE. In one embodiment, a method includes a second UE initiating a first procedure to establish a one-to-one connection with a first UE for unicast communication between the first UE and the second UE or for inter-UE communication between the first UE and a third UE via the second UE, or a second procedure to establish a one-to-one connection with the first UE for UE-to-network communication between the first UE and a network node via the second UE. The method also includes the second UE transmitting a first PC5-S message to the first UE for completing a first procedure for establishing a one-to-one connection with the first UE for unicast communication or inter-UE communication, wherein the first PC5-S message includes quality of service (QoS) information for the unicast communication or the inter-UE communication. The method also includes the second UE transmitting a second PC5-S message to the first UE for completing a second procedure for establishing a one-to-one connection with the first UE for UE-to-network communication, wherein the second PC5-S message does not include any QoS information for the UE-to-network communication.

Drawings

Fig. 1 illustrates a diagram of a wireless communication system according to an example embodiment.

Fig. 2 is a block diagram of a transmitter system (also referred to as an access network) and a receiver system (also referred to as a user equipment or UE) according to an example embodiment.

Fig. 3 is a functional block diagram of a communication system according to an exemplary embodiment.

FIG. 4 is a functional block diagram of the program code of FIG. 3 according to one exemplary embodiment.

Fig. 5 is a reproduction of fig. 5.2.1.4-1 of 3GPP 23.287 V16.2.0.

Fig. 6 is a reproduction of fig. 6.3.3.1-1 of 3GPP 23.287 V16.2.0.

Fig. 7 is a reproduction of fig. 6.3.3.2-1 of 3GPP TS 23.287 V16.2.0.

Fig. 8 is a reproduction of fig. 6.3.3.3-1 of 3GPP TS 23.287 V16.2.0.

Fig. 9 is a reproduction of fig. 6.3.3.4-1 of 3GPP TS 23.287 V16.2.0.

Fig. 10 is a reproduction of fig. 6.3.3.5-1 of 3GPP TS 23.287 V16.2.0.

Fig. 11 is a reproduction of fig. 6.1.2.2.2 of 3GPP TS 24.587 V16.1.0.

Fig. 12 is a reproduction of fig. 6.1.2.6.2 of 3GPP TS 24.587 V16.1.0.

Fig. 13 is a reproduction of fig. 6.1.2.7.2 of 3GPP TS 24.587 V16.1.0.

Fig. 14 is a reproduction of table 7.3.2.1.1 of 3GPP TS 24.587 V16.1.0.

Fig. 15 is a reproduction of table 7.3.14.1.1 of 3GPP TS 24.587 V16.1.0.

Fig. 16 is a reproduction of 3GPP TR 23.752 V0.5.0 fig. 5.3.1-1.

Fig. 17 is a reproduction of fig. 5.3.1-2 of 3GPP TR 23.752 V0.5.0.

Fig. 18 is a reproduction of fig. 5.3.1-3 of 3GPP TR 23.752 V0.5.0.

Fig. 19 is a reproduction of fig. 6.6.1-1 of 3GPP TR 23.752 V0.5.0.

Fig. 20 is a reproduction of fig. 6.6.1-2 of 3GPP TR 23.752 V0.5.0.

Fig. 21 is a reproduction of fig. 6.6.2-1 of 3GPP TR 23.752 V0.5.0.

Fig. 22 is a reproduction of fig. 6.23.1-1 of 3GPP TR 23.752 V0.5.0.

Fig. 23 is a reproduction of fig. 6.23.2-2 of 3GPP TR 23.752 V0.5.0.

Fig. 24 is a reproduction of fig. 6.23.2-3 of 3GPP TR 23.752 V0.5.0.

Fig. 25 is a reproduction of fig. 6.23.3-1 of 3GPP TR 23.752 V0.5.0.

Fig. 26 is a reproduction of fig. 6.24.1-1 of 3GPP TR 23.752 V0.5.0.

Fig. 27 is a reproduction of fig. 6.25.2-1 of 3GPP TR 23.752 V0.5.0.

Fig. 28 is a reproduction of fig. 6.25.3-1 of 3GPP TR 23.752 V0.5.0.

Fig. 29 is a flowchart in accordance with an exemplary embodiment.

FIG. 30 is a flowchart in accordance with an exemplary embodiment.

FIG. 31 is a flowchart in accordance with an exemplary embodiment.

Detailed Description

The exemplary wireless communication systems and apparatus described below employ wireless communication systems that support broadcast services. Wireless communication systems are widely deployed to provide various types of communication such as voice, data, and so on. These systems may be based on Code Division Multiple Access (CDMA), time Division Multiple Access (TDMA), orthogonal Frequency Division Multiple Access (OFDMA), 3GPP long term evolution (Long Term Evolution, LTE) wireless access, 3GPP long term evolution advanced (Long Term Evolution Advanced, LTE-a), 3GPP2 ultra mobile broadband (Ultra Mobile Broadband, UMB), wiMax, 3GPP New Radio (NR), or some other modulation technique.

In particular, the exemplary wireless communication systems and devices described below may be designed to support one or more standards, e.g., standards provided by an association named "third generation partnership project" (referred to herein as 3 GPP), including: TS 23.287 V16.2.0, "architecture enhancement (version 16) for 5G systems (5 GS) supporting Vehicle-to-Everivating (V2X) services"; TS 24.587 V16.1.0, "Vehicle-to-Everiving, V2X service in 5G System (5 GS); stage 3 (version 16) "; and TR 23.752 v0.5.0, "study of proximity services (ProSe) based system enhancements in 5G system (5 GS) (release 17)". The standards and documents listed above are hereby expressly incorporated by reference in their entirety.

Fig. 1 illustrates a multiple access wireless communication system according to one embodiment of the present invention. The access network 100 (AN) includes multiple antenna groups, one including 104 and 106, another including 108 and 110, and yet another including 112 and 114. In fig. 1, only two antennas are shown for each antenna group, however, more or fewer antennas may be utilized for each antenna group. An Access terminal 116 (AT) is in communication with

antennas

112 and 114, where

antennas

112 and 114 transmit information to Access terminal 116 over forward link 120 and receive information from Access terminal 116 over reverse link 118. An Access Terminal (AT) 122 is in communication with

antennas

106 and 108, where

antennas

106 and 108 transmit information to Access Terminal (AT) 122 over a forward link 126 and receive information from Access Terminal (AT) 122 over a reverse link 124. In an FDD system,

communication links

118, 120, 124 and 126 may use different frequency for communication. For example, forward link 120 may use a different frequency than that used by reverse link 118.

The antennas of each group and/or the area in which they are designed to communicate are often referred to as a sector of the access network. In an embodiment, antenna groups each are designed to communicate to access terminals in a sector of the areas covered by access network 100.

In communication over

forward links

120 and 126, the transmit antennas of access network 100 may utilize beamforming in order to improve signal-to-noise ratio of forward links for the

different access terminals

116 and 122. And, the access network using beamforming to transmit to access terminals scattered randomly through its coverage causes less interference to access terminals in neighboring cells than an access network transmitting through a single antenna to all its access terminals.

AN Access Network (AN) may be a fixed station or base station used for communicating with the terminals and may also be referred to as AN access point, a Node B, a base station, AN enhanced base station, AN evolved Node B (eNB), a network Node, a network, or some other terminology. An Access Terminal (AT) may also be referred to as a User Equipment (UE), a wireless communication device, a terminal, an access terminal, or some other terminology.

Fig. 2 is a simplified block diagram of an embodiment of a transmitter system 210 (also referred to as an access network) and a receiver system 250 (also referred to as an Access Terminal (AT) or User Equipment (UE)) in a MIMO system 200. At the transmitter system 210, traffic data for a number of data streams is provided from a data source 212 to a Transmit (TX) data processor 214.

In one embodiment, each data stream is transmitted through a respective transmit antenna. TX data processor 214 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide coded data.

The coded data for each data stream may be multiplexed with pilot data using OFDM techniques. The pilot data is typically a known data pattern that is processed in a known manner and may be used at the receiver system to estimate the channel response. The multiplexed pilot and coded data for each data stream is then modulated (i.e., symbol mapped) based on a particular modulation scheme (e.g., BPSK, QPSK, M-PSK or M-QAM) selected for that data stream to provide modulation symbols. Instructions executed by processor 230 may determine the data rate, coding, and modulation for each data stream.

The modulation symbols for all data streams are then provided to a TX MIMO processor 220, which may further process the modulation symbols (e.g., for OFDM). TX MIMO processor 220 then applies N _T Providing the modulated symbol streams to N _T Transmitters (TMTR) 222a through 222t. In certain embodiments, TX MIMO processor 220 applies beamforming weights to the symbols of the data streams and to the antenna from which the symbol is being transmitted.

Each transmitter 222 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (e.g., amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. Then respectively from N _T The antennas 224a through 224t transmit N from the transmitters 222a through 222t _T A modulated signal.

At the receiver system 250, the signal is represented by N _R Each antenna 252 a-252 r receives the transmitted modulated signals and provides the signals received from each antenna 252 to a respective receiver (RCVR) 254 a-254 r. Each receiver 254 conditions (e.g., filters, amplifies, and downconverts) a respective received signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding "received" symbol stream.

RX data processor 260 then proceeds to process the data from N based on a particular receiver _R The N is received and processed by a plurality of receivers 254 _R Providing N by receiving symbol streams _T The "detected"symbol stream". RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. The processing by RX data processor 260 is complementary to that performed by TX MIMO processor 220 and TX data processor 214 at transmitter system 210.

The processor 270 periodically determines which pre-coding matrix to use (discussed below). Processor 270 formulates a reverse link message comprising a matrix index portion and a rank value portion.

The reverse link message may comprise various types of information regarding the communication link and/or the received data stream. The reverse link message is then processed by a TX data processor 238, which also receives traffic data for a number of data streams from a data source 236, modulated by a modulator 280, conditioned by transmitters 254a through 254r, and transmitted back to transmitter system 210.

At transmitter system 210, the modulated signals from receiver system 250 are received by antennas 224, conditioned by receivers 222, demodulated by a demodulator 240, and processed by a RX data processor 242 to extract the reverse link message transmitted by receiver system 250. Processor 230 then determines which pre-coding matrix to use to determine the beamforming weights and then processes the extracted message.

Turning to fig. 3, this figure shows an alternative simplified functional block diagram of a communication device according to one embodiment of the present invention. As shown in fig. 3, a communication device 300 in a wireless communication system may be utilized for implementing UEs (or ATs) 116 and 122 in fig. 1 or base station (or AN) 100 in fig. 1, and the wireless communication system is preferably AN NR system. The communication device 300 may include an input device 302, an output device 304, a control circuit 306, a central processing unit (central processing unit, CPU) 308, a memory 310, program code 312, and a transceiver 314. The control circuit 306 executes the program code 312 in the memory 310 via the CPU 308, thereby controlling the operation of the communication device 300. The communication device 300 may receive signals input by a user through an input device 302 (e.g., a keyboard or keypad) and may output images and sounds through an output device 304 (e.g., a display or speaker). The transceiver 314 is used to receive and transmit wireless signals, pass the received signals to the control circuit 306, and wirelessly output signals generated by the control circuit 306. The AN 100 of fig. 1 may also be implemented with a communication device 300 in a wireless communication system.

Fig. 4 is a simplified block diagram of the program code 312 shown in fig. 3 according to one embodiment of the invention. In this embodiment, program code 312 includes an application layer 400, a layer 3 portion 402, and a layer 2 portion 404, and is coupled to a layer 1 portion 406. Layer 3 portion 402 typically performs radio resource control. Layer 2 portion 404 typically performs link control. Layer 1 portion 406 typically performs physical connections.

3GPP TS 23.287 describes the following:

5.2.1.4 unicast mode communication over PC5 reference point

The NR-based PC5 reference point supports only unicast communication modes. Fig. 5.2.1.4-1 shows an example of a PC5 unicast link.

Fig. 5.2.1.4-1 titled "example of PC5 unicast link" of 3GPP TS 23.287 V16.2.0 is reproduced as fig. 5]

When carrying V2X communications over a PC5 unicast link, the following principles apply:

the PC5 unicast link between two UEs allows V2X communication between one or more pairs of peer V2X services among these UEs. All V2X services in the UE using the same PC5 unicast link use the same application layer ID.

Note 1: due to privacy, the application layer ID may change over time as described in clauses 5.6.1.1 and 6.3.3.2. This does not result in re-establishment of the PC5 unicast link. The UE triggers a link identifier update procedure as specified in clause 6.3.3.2.

One PC5 unicast link supports one or more V2X service types (e.g., PSID or ITS-AID), provided that these V2X service types are associated with at least a pair of equal application layer IDs for this PC5 unicast link. For example, as shown in FIG. 5.2.1.4-1, UE A and UE B have two PC5 unicast links, one between peer application layer ID 1/UE A and application layer ID 2/UE B and one between peer application layer ID 3/UE A and application layer ID 4/UE B.

And (2) injection: the source UE is not required to know whether different target application layer IDs on different PC5 unicast links belong to the same target UE.

The PC5 unicast link supports V2X communication using a single network layer protocol such as IP or non-IP.

The PC5 unicast link supports per flow QoS model as specified in clause 5.4.1.

When an application layer in the UE initiates data transfer for a V2X service type requiring a unicast communication mode through the PC5 reference point:

-if the network layer protocols of the pair of equal application layer IDs and this PC5 unicast link are the same as those required by the application layer in the UE for this V2X service, the UE will reuse the existing PC5 unicast link and modify the existing PC5 unicast link as specified in section 6.3.3.4 to add this V2X service; otherwise

The UE will trigger the establishment of a new PC5 unicast link as specified in clause 6.3.3.1.

After successfully establishing the PC5 unicast link, UE a and UE B use the same pair of layer 2 IDs for subsequent PC5-S signaling message exchanges and V2X service data transfer, as specified in section 5.6.1.4. The V2X layer of the transmitting UE indicates to the AS layer whether the transmission is for a PC5-S signaling message (i.e., direct communication request/accept, link identifier update request/response/acknowledgement, disconnect request/response, link modification request/accept) or V2X service data.

For each PC5 unicast link, the UE self-assigns a different PC5 link identifier that uniquely identifies the PC5 unicast link in the UE over the lifetime of the PC5 unicast link. Each PC5 unicast link is associated with a unicast link profile comprising:

-V2X service type (e.g. PSID or ITS-AID); and

-an application layer ID and a layer 2ID of UE a; and

-an application layer ID and a layer 2ID of UE B; and

-a network layer protocol used on a PC5 unicast link; and

-for each V2X service type, a set of PC5 QoS flow identifiers (PC 5 QoS Flow Identifier, PFI). Each PFI is associated with a QoS parameter (i.e., PQI).

For privacy reasons, the application layer ID and layer 2ID may change during the lifetime of the PC5 unicast link as described in clauses 5.6.1.1 and 6.3.3.2, and if so, should be updated in the unicast link profile accordingly. The UE indicates a PC5 unicast link to the V2X application layer using the PC5 link identifier, so the V2X application layer identifies the corresponding PC5 unicast link even if there is more than one unicast link associated with one V2X service type (e.g., the UE establishes multiple unicast links with multiple UEs for the same V2X service type).

The unicast link profile should be updated accordingly after a layer 2 link modification to the established PC5 unicast link as specified in clause 6.3.3.4 or a layer 2 link identifier update as specified in clause 6.3.3.2.

The V2X service information and QoS information are carried in PC5-S signaling messages and exchanged between two UEs as specified in clause 6.3.3. Based on the replacement information, the PFI is used to identify the V2X service. When the receiving UE receives V2X service data through the established PC5 unicast link, the receiving UE determines an appropriate V2X service based on the PFI to forward the received V2X service data to an upper layer.

Upon receiving an indication from the AS layer to release the PC5-RRC connection due to RLF, the V2X layer in the UE locally releases the PC5 unicast link associated with this PC5-RRC connection. The AS layer uses the PC5 link identifier to indicate the PC5 unicast link that releases the PC5-RRC connection.

When the PC5 unicast link has been released AS specified in clause 6.3.3.3, the V2X layer of each UE for the PC5 unicast link notifies the AS layer that the PC5 unicast link has been released. The V2X layer indicates the released unicast link using the PC5 link identifier.

[...]

5.6.1.4 identifier for unicast mode V2X communication over PC5 reference point

For V2X communication in unicast mode through the PC5 reference point, the destination layer 2ID used depends on the communicating peer. The layer 2ID of the communication peer identified by the application layer ID may be discovered during establishment of the PC5 unicast link, or known to the UE via previous V2X communication (e.g., an existing or previous unicast link to the same application layer ID), or obtained from an application layer service announcement. The initial signaling for establishing the PC5 unicast link may use the known layer 2ID of the communication peer or a default destination layer 2ID associated with the V2X service type (e.g., PSID/ITS-AID) configured for PC5 unicast link establishment, as specified in section 5.1.2.1. During the PC5 unicast link establishment procedure, the layer 2ID is exchanged and should be used for future communication between two UEs, as specified in section 6.3.3.1.

The application layer ID is associated with one or more V2X applications within the UE. If a UE has more than one application layer ID, each application layer ID of the same UE may be considered as an application layer ID of a different UE from the perspective of a peer UE.

Since the V2X application layer does not use the layer 2ID, the UE maintains a mapping between the application layer ID and the source layer 2ID for the PC5 unicast link. This allows changing the source layer 2ID without interrupting the V2X application.

When the application layer ID changes, if the link is used for V2X communication with the changed application layer ID, the source layer 2ID of the PC5 unicast link should be changed.

Updating the new identifier of the source UE to the peer UE for the established unicast link may cause the peer UE to change its layer 2ID and optionally IP address/prefix (if IP communication is generally used as defined in clause 6.3.3.2) based on the privacy configuration as specified in clause 5.1.2.1.

The UE may establish multiple PC5 unicast links with peer UEs and use the same or different source layer 2 IDs for these PC5 unicast links.

[...]

6.3.3 unicast mode V2X communication through PC5 reference Point

6.3.3.1 establishing a layer 2 link through a PC5 reference point

In order to perform unicast mode V2X communication through the PC5 reference point, the UE is configured with related information as described in section 5.1.2.1.

Fig. 6.3.3.1-1 shows a layer 2 link setup procedure for unicast mode of V2X communication through a PC5 reference point.

Fig. 6.3.3.1-1 entitled "layer 2 Link setup procedure" of 3GPP TS 23.287 V16.2.0 is reproduced as fig. 6]

1. As specified in clause 5.6.1.4, the UE determines the destination layer 2ID for signaling reception for PC5 unicast link establishment. The UE is configured with the destination layer 2ID as specified in clause 5.1.2.1.

The V2X application layer in ue-1 provides application information for PC5 unicast communication. The application information contains the V2X service type (e.g., PSID or ITS-AID) of the V2X application and the application layer ID of the originating UE. The application information may include an application layer ID of the target UE.

The V2X application layer in UE-1 may provide V2X application requirements for this unicast communication. As specified in clause 5.4.1.4, UE-1 determines the PC5 QoS parameters and PFI.

If UE-1 decides to reuse the existing PC5 unicast link as specified in clause 5.2.1.4, then the UE initiates a layer 2 link modification procedure as specified in clause 6.3.3.4.

Ue-1 sends a direct communication request message to initiate a unicast layer 2 link setup procedure. The direct communication request message includes:

-source user information: the application layer ID of the UE is initiated (i.e., the application layer ID of UE-1).

-if the V2X application layer provides the application layer ID of the target UE in step 2, then the following information is contained:

-target user information: the application layer ID of the target UE (i.e., the application layer ID of UE-2).

-V2X service information: information about V2X services (e.g., PSID or ITS-AID) requesting layer 2 link establishment.

-security information: information for establishing security.

Note 1: the security information and the necessary protection for the source and target user information are defined by the SA WG 3.

The source layer 2ID and the destination layer 2ID for transmitting the direct communication request message are determined as specified in sections 5.6.1.1 and 5.6.1.4. The destination layer 2ID may be a broadcast or unicast layer 2ID. When using the unicast layer 2ID, the target user information should be contained in the direct communication request message.

The UE-1 transmits a direct communication request message via the PC5 broadcast or unicast using the source layer 2ID and the destination layer 2ID.

4. The security of UE-1 is established as follows:

4a. If the target user information is included in the direct communication request message, the target UE (i.e., UE-2) responds by establishing security with UE-1.

4b. If the target user information is not contained in the direct communication request message, the UE interested in V2X service notified through PC5 unicast link usage with UE-1 responds by establishing security with UE-1.

And (2) injection: signaling for security procedures is defined by the SA WG 3.

When security protection is enabled, UE-1 sends the following information to the target UE:

-in case IP communication is used:

-IP address configuration: for IP communications, this link requires an IP address configuration, and it indicates one of the following values:

-an "IPv6 router", i.e. acting as an IPv6 router if only the IPv6 address allocation mechanism is supported by the initiating UE; or (b)

"IPv6 address allocation not supported", if the IPv6 address allocation mechanism is not supported by the initiating UE.

-link local IPv6 address: based on the link local IPv6 address formed locally by RFC 4862[21], if UE-1 does not support IPv6IP address allocation mechanism, i.e. IP address configuration indicates "IPv6 address allocation not supported".

QoS information: information about PC5 QoS flows. For each PC5 QoS flow, the PFI and the corresponding PC5 QoS parameters (i.e., PQI and conditionally other parameters, e.g., MFBR/GFBR, etc.).

The source layer 2ID for the security setup procedure is determined as specified in clauses 5.6.1.1 and 5.6.1.4. The destination layer 2ID is set to the source layer 2ID of the received direct communication request message.

Upon receiving the security setup procedure message, UE-1 obtains the layer 2ID of the peer UE for future communications for signaling and data traffic for this unicast link.

5. The target UE that has successfully established security with UE-1 sends a direct communication accept message to UE-1:

(UE-oriented layer 2 link establishment) if the direct communication request message contains target user information, then the target UE, i.e., UE-2, responds with a direct communication accept message if the application layer ID for UE-2 matches.

(layer 2 link establishment towards V2X service) if the target user information is not contained in the direct communication request message, the UE interested in using the notified V2X service responds to the request by sending a direct communication accept message (UE-2 and UE-4 in fig. 6.3.3.1-1).

The direct communication accept message includes:

-source user information: an application layer ID of the UE transmitting the direct communication accept message.

QoS information: information about PC5 QoS flows. For each PC5 QoS flow, the PFI and the corresponding PC5 QoS parameters requested by UE-1 (i.e., PQI and other parameters of the conditionality, such as MFBR/GFBR, etc.).

-in case IP communication is used:

"IPv6 router", which acts as IPv6 router if IPv6 address allocation mechanism is supported by target UE; or (b)

"does not support IPv6 address allocation", if the IPv6 address allocation mechanism is not supported by the initiating UE.

-link local IPv6 address: based on the link local IPv6 address formed locally by RFC 4862[21], if the target UE does not support the IPv6IP address allocation mechanism, i.e., the IP address configuration indicates "IPv6 address allocation is not supported", and UE-1 includes the link local IPv6 address in the direct communication request message. The target UE should contain a non-conflicting link local IPv6 address.

If two UEs (i.e., the initiating UE and the target UE) are selected to use the link-local IPv6 address, they will deactivate the dual address detection defined in RFC 4862[21 ].

And (3) injection: when the initiating UE or the target UE indicates support for the IPv6 router, the corresponding address configuration procedure will be implemented after the layer 2 link is established and the link local IPv6 address is ignored.

The V2X layer of the UE that established the PC5 unicast link passes the PC5 link identifier assigned to the unicast link and information related to the PC5 unicast link down to the AS layer. The information related to the PC5 unicast link contains layer 2ID information (i.e., source layer 2ID and destination layer 2 ID). This enables the AS layer to maintain PC5 link identifiers and PC5 unicast link related information.

6. V2X service data is transmitted over the established unicast link as follows:

the PC5 link identifier and PFI and V2X service data are provided to the AS layer.

In addition, layer 2ID information (i.e., source layer 2ID and destination layer 2 ID) is optionally provided to the AS layer.

And (4) injection: layer 2ID information is provided to the AS layer by the UE implementation.

UE-1 transmits V2X service data using a source layer 2ID (i.e., layer 2ID of UE-1 for this unicast link) and a destination layer 2ID (i.e., layer 2ID of peer UE for this unicast link).

And (5) injection: the PC5 unicast link is bi-directional, so that a peer UE of UE-1 may send V2X service data to UE-1 over the unicast link with UE-1.

6.3.3.2 link identifier update for unicast links

Fig. 6.3.3.2-1 shows a link identifier update procedure for a unicast link. Due to privacy requirements, the identifiers (e.g., application layer ID, source layer 2ID, and IP address/prefix) used for unicast mode V2X communications through the PC5 reference point should be changed over time, as specified in sections 5.6.1.1 and 5.6.1.4. This procedure is used to update and exchange new identifiers between the source and peer UEs for the unicast link and then re-use the new identifiers, thereby preventing service interruption.

If the UE has multiple unicast links using the same application layer ID or layer 2ID, the UE needs to perform a link identifier update procedure through each of the unicast links.

Fig. 6.3.3.2-1 entitled "link identifier update procedure" of [3GPP TS 23.287 V16.2.0 ] is reproduced as fig. 7]

UE-1 and UE-2 have unicast links established as described in clause 6.3.3.1.

1. For example, UE-1 decides to change its identifier due to an application layer ID change or upon expiration of a timer. UE-1 generates its new layer 2ID using the old identifier and sends a link identifier update request message to UE-2.

The link identifier update request message contains the new identifier to be used (containing the new layer 2ID, security information, optionally the new application layer ID and optionally the new IP address/prefix in case IP communication is used). The new identifier should be encrypted to protect privacy. After sending the link identifier update request, UE-1 remains sending data traffic to UE-2 with the old identifier until UE-1 sends a link identifier update acknowledgement to UE-2.

Note 1: a timer runs on each source layer 2-ID.

And (2) injection: when one of the two UEs acts as an IPv6 router and the IP address/prefix also needs to be changed, as described in section 5.2.1.5, the corresponding address configuration procedure will be carried out after the link identifier update procedure.

2. Upon receiving the link identifier update request message, UE-2 may also decide to change its identifier based on the privacy configuration as specified in clause 5.1.2.1. If the UE-2 decides to change its identifier, the UE-2 responds with a link identifier update response message containing the new identifier to be used (containing the new layer 2ID, security information, optionally the new application layer ID, and optionally the new IP address/prefix in case IP communication is used). The new identifier should be encrypted to protect privacy. The link identifier update response message is sent using the old identifier. UE-2 continues to receive traffic from UE-1 with the old layer 2ID until UE-2 receives traffic from UE-1 with the new layer 2 ID. After sending the link identifier update response, UE-2 remains sending data traffic to UE-1 with the old identifier until UE-2 receives a link identifier update confirm message from UE-1.

3. Upon receiving the link identifier update response message, UE-1 responds with a link identifier update confirm message containing the new identifier from UE-2 received on the link identifier update response message. The link identifier update confirm message is sent using the old identifier. UE-1 continues to receive traffic from UE-2 with the old layer 2ID until UE-1 receives traffic from UE-2 with the new layer 2 ID.

The V2X layer of UE-1 passes the PC5 link identifier for the unicast link and the updated layer 2ID (i.e., the new layer 2ID for the source UE-1 and the new layer 2ID for the destination UE-2) down to the AS layer. This enables the AS layer to update the provided layer 2ID for the unicast link.

For this unicast link, UE-1 starts to use its new identifier and the new identifier of UE-2.

The V2X layer of UE-2 passes the PC5 link identifier and updated layer 2ID for the unicast link (i.e., new layer 2ID for source UE-2 and new layer 2ID for destination UE-1) down to the AS layer. This enables the AS layer to update the provided layer 2ID for the unicast link.

For this unicast link, UE-2 starts to use its new identifier and the new identifier of UE-1.

And (3) injection: the security information in the above message also needs to be updated simultaneously with the layer 2ID. This is defined in TS 33.536[26 ].

6.3.3.3 layer 2 link release via PC5 reference point

Fig. 6.3.3.3-1 shows a layer 2 link release procedure through a PC5 reference point.

Fig. 6.3.3.3-1 entitled "layer 2 Link Release procedure" of 3GPP TS 23.287 V16.2.0 is reproduced as fig. 8]

UE-1 and UE-2 have unicast links established as described in clause 6.3.3.1.

UE-1 sends a disconnect request message to UE-2 to release the layer 2 link and delete all context data associated with the layer 2 link.

2. Upon receiving the disconnect request message, UE-2 may respond to the disconnect response message and delete all context data associated with the layer 2 link.

The V2X layer of each UE informs the AS layer that the unicast link has been released. The V2X layer indicates the released unicast link using the PC5 link identifier. This enables the AS layer to delete the context associated with the released unicast link.

6.3.3.4 layer 2 link modification for unicast links

Fig. 6.3.3.4-1 shows a layer 2 link modification procedure for a unicast link. This procedure is used to:

adding a new V2X service to the existing PC5 unicast link.

-removing V2X services from existing PC5 unicast links.

-adding a new PC5 QoS flow in an existing PC5 unicast link.

-modifying existing PC5 QoS flows in existing PC5 unicast links.

-removing existing PC5 QoS flows in existing PC5 unicast links.

Fig. 6.3.3.4-1 entitled "layer 2 Link modification procedure" of [3GPP TS 23.287 V16.2.0 ] is reproduced as fig. 9]

UE-1 and UE-2 have unicast links established as described in clause 6.3.3.1.

The V2X application layer in ue-1 provides application information for PC5 unicast communication. The application information includes a V2X service type (e.g., PSID or ITS-AID) of the V2X application and an application layer ID of the originating UE. The application information may include an application layer ID of the target UE. If UE-1 decides to reuse the existing PC5 unicast link as specified in clause 5.2.1.4, and thus decides to modify the unicast link established with UE-2, UE-1 sends a link modification request to UE-2.

The link modification request message contains:

a) To add a new V2X service to the existing PC5 unicast link:

-V2X service information: information about the V2X service to be added (e.g., PSID or ITS-AID).

QoS information: information about PC5 QoS flows for each V2X service to be added. For each PC5 QoS flow, the PFI and the corresponding PC5 QoS parameters (i.e., PQI and conditionally other parameters, e.g., MFBR/GFBR, etc.).

b) To remove V2X services from the existing PC5 unicast link:

-V2X service information: information about the V2X service to be removed (e.g., PSID or ITS-AID).

c) To add a new PC5 QoS flow in an existing PC5 unicast link:

-V2X service information: information about V2X services (e.g., PSID or ITS-AID) that a new QoS flow needs to be added.

QoS information: information about the PC5 QoS flows to be modified. For each PC5 QoS flow, the PFI and the corresponding PC5 QoS parameters (i.e., PQI and conditionally other parameters, e.g., MFBR/GFBR, etc.).

d) To modify the PC5 QoS flows in the existing PC5 unicast link:

e) To remove the PC5 QoS flows in the existing PC5 unicast link:

-PFIs。

ue-2 responds to the link modification accept message.

The link modification accept message contains:

for case a), case c) and case d) described in step 1:

The V2X layer of each UE provides information about the unicast link modification to the AS layer. This enables the AS layer to update the context associated with the modified unicast link.

6.3.3.5 layer 2 link maintenance via PC5 reference point

The PC5 signaling protocol should support a keep-alive function for detecting whether a particular PC5 unicast link is still active. Either side of the PC5 unicast link may initiate a layer 2 link maintenance procedure (i.e., a keep-alive procedure) based on, for example, a trigger from the AS layer or an internal timer. If the data is successfully received over the PC5 unicast link, the UE should minimize keep-alive signaling, e.g., cancel the procedure.

Fig. 6.3.3.5-1 entitled "layer 2 Link maintenance procedure" of 3GPP TS 23.287 V16.2.0 is reproduced as fig. 10]

UE-1 and UE-2 have unicast links established as described in clause 6.3.3.1.

1. Based on the trigger condition, UE-1 sends a keep-alive message to UE-2 to determine the state of the PC5 unicast link.

Note 1: leaving phase 3 to determine the exact trigger for keep-alive messages. For example, the trigger may be based on a timer associated with the layer 2 link. The timer may be reset with a successful receipt event defined by TS 38.300[11 ].

2. After receiving the keep-alive message, UE-2 responds to the keep-alive Ack message.

The UE initiating the keep-alive procedure should determine follow-up actions based on the result of the signaling, such as to proceed with the implicit layer 2 link release.

And (2) injection: leaving to stage 3 to determine follow-up action. For example, if a successful reception event is received in time, the layer 2 link release may also be cancelled.

3GPP TS 24.587 describes some procedures related to unicast link communications as follows:

6.1.2.2 PC5 unicast link establishment program

6.1.2.2.1 general rule

The PC5 unicast link setup procedure is used to set up a PC5 unicast link between two UEs. The UE that sends the request message is referred to as the "initiating UE" and the other UE is referred to as the "target UE". The maximum number of NR PC5 unicast links established in the UE at a time should not exceed the implementation specific maximum number of established NR PC5 unicast links.

And (3) injection: the proposed maximum number of established NR PC5 unicast links is 8.

[...]

6.1.2.2.2 initiates a PC5 unicast link setup procedure by an initiating UE

[...]

The initiating UE should meet the following preconditions before initiating this procedure:

a) A request from an upper layer for transmitting a packet of the V2X service through the PC 5;

b) The communication mode is a unicast mode (e.g., preconfigured or indicated by an upper layer as specified in clause 5.2.3);

c) The link layer identifier for the initiating UE (i.e., the layer 2ID for unicast communication) is available (e.g., preconfigured or self-assigned) and is not used by other existing PC5 unicast links within the initiating UE;

d) The link layer identifier for unicast initial signaling (i.e., the destination layer 2ID for unicast initial signaling) may be used to initiate the UE (e.g., preconfigured, obtained as specified in clause 5.2.3, or known via previous V2X communications);

note that: in the case where different V2X services map to different default destination layer 2 IDs, when the initiating UE wishes to establish a single unicast link that is available for more than one V2X service type, the UE may select any one of the default destination layer 2 IDs for unicast initial signaling.

e) The originating UE is authorized to conduct V2X communication through a PC5 of NR-PCs 5 in the serving PLMN or has valid authorization for V2X communication through a PC5 of NR-PCs 5 when not served by E-UTRA and not served by NR; and

f) There is no existing PC5 unicast link for a pair of equal application layer IDs, or there is an existing PC5 unicast link for a pair of equal application layer IDs and the network layer protocol of the existing PC5 unicast link is different from the network layer protocol required for this V2X service at the upper layer in the initiating UE.

g) The number of established PC5 unicast links is less than the implementation-specific maximum number of established NR PC5 unicast links allowed in the UE at a time.

After receiving traffic data or requests from upper layers, the initiating UE should derive the PC5 QoS parameters and assign PQFI for establishing the PC5 QoS flow as specified in clause 6.1.2.12.

To initiate the PC5 unicast link setup procedure, the initiating UE should form a direct link setup request message. Initiating UE:

a) Source user information set to an application layer ID of the originating UE received from an upper layer should be included;

b) Should contain the V2X service identifier received from the upper layer;

c) A target user information set to be set to an application layer ID of the target UE received from an upper layer should be included;

d) The key establishment information container should be included in case the UE PC5 unicast signaling integrity protection policy is set to "signaling integrity protection is required" or "preferred signaling integrity protection", and the key establishment information container may be included in case the UE PC5 unicast signaling integrity protection policy is set to "signaling integrity protection is not required";

Note 1: the key establishment information container is provided by an upper layer.

e) If the UE PC5 unicast signaling integrity protection policy is set to "require signaling integrity protection" or "preferred signaling integrity protection", then the nonce_1 set should be included to the 128-bit temporary value generated by the initiating UE for session key establishment over this PC5 unicast link;

f) A list of algorithms that should contain its UE security capabilities, indicating that the initiating UE supports secure establishment of this PC5 unicast link;

g) If the UE PC5 unicast signaling integrity protection policy is set to "need signaling integrity protection" or "preferred signaling integrity protection", then it should be included as 3GPP TS 33.536[20]In provision of K selected by initiating UE _NRP-sess 8 MSBs of ID;

h) If the originating UE has an existing K for the target UE _NRP Then may contain K _NRP An ID; and

i) Its UE PC5 unicast signaling security policy should be included.

After generating the direct link setup request message, the initiating UE should pass this message to the lower layer to transmit with the layer 2ID of the initiating UE for unicast communication and the destination layer 2ID for unicast initial signaling, and start the timer T5000. While timer T5000 is running, the UE should not send a new direct link setup request message to the same target UE identified by the same application layer ID.

And (2) injection: to ensure successful PC5 unicast link establishment, T5000 should be set to a value greater than the sum of T5006 and T5007.

Fig. 6.1.2.2.2 entitled "PC5 unicast link establishment procedure" of [3GPP TS 24.587 V16.1.0 ] is reproduced as fig. 11]

6.1.2.2.3 accepting PC5 unicast Link setup procedure by target UE

Upon receiving the direct link setup request message, if the target UE accepts the request, the target UE should uniquely assign a PC5 link identifier, create a PC5 unicast link context and assign a layer 2ID for this PC5 unicast link. The target UE should then store this assigned layer 2ID and the source layer 2ID used in the transmission of this message provided by the lower layers in the PC5 unicast link context.

If:

a) The target user information IE is contained in the direct link setup request message and this IE contains the application layer ID of the target UE; or (b)

b) The target user information IE is not included in the direct link setup request message and the target UE is interested in the V2X service identified by the V2X service identifier IE in the direct link setup request message;

then the target UE should:

a) Based on K contained in the direct link setup request message _NRP ID identifies existing K _NRP The method comprises the steps of carrying out a first treatment on the surface of the Or (b)

b) If K _NRP The ID is not included in the direct link setup request message, or the target UE does not have K for inclusion in the direct link setup request message _NRP Existing K of ID _NRP Or the target UE wishes to derive a new K _NRP Then a new K is derived _NRP . This may require execution of one or more PC5 unicast link authentication procedures as specified in section 6.1.2.6.

Note that: how many times the PC5 unicast link authentication procedure needs to be performed to derive a new K _NRP Depending on the authentication method used.

In the identification of the existing K _NRP Or derive a new K _NRP Thereafter, the target UE should initiate the PC5 unicast link security mode control procedure as specified in section 6.1.2.7.

After successful completion of the PC5 unicast link security mode control procedure, the target UE checks in case of IP communication if there is at least one public IP address configuration option supported by both the originating UE and the target UE in order to determine if the direct link setup request message can be accepted.

If the target UE accepts the PC5 unicast link setup procedure, the target UE should form a direct link setup accept message. Target UE:

a) Source user information set to an application layer ID of the target UE received from an upper layer should be included;

b) Shall contain PQFI and corresponding PC5 QoS parameters;

c) If IP communication is used, an IP address configuration IE set to one of the following values should be included:

1) "IPv6 router" if the target UE supports IPv6 address allocation mechanism, i.e., acts as an IPv6 router; or (b)

2) "IPv6 address assignment is not supported" if IPv6 address assignment mechanism is not supported by the target UE;

d) If the IP address configuration IE is set to "not supporting IPv6 address assignment" and the received direct link setup request message contains a link local IPv6 address IE, then it should contain a link local IPv6 address formed locally based on IETF RFC 4862[16 ]; and

e) The configuration of UE PC5 unicast user plane security protection based on agreed user plane security policies should be included, as specified in 3GPP TS 33.536[20.

After generating the direct link setup accept message, the initiating UE should pass this message to the lower layer for transmission along with the layer 2ID of the initiating UE for unicast communication and the layer 2ID of the target UE for unicast communication.

After sending the direct link setup accept message, the target UE should provide the following information to the lower layer along with the layer 2ID so that the lower layer can handle the incoming PC5 signaling or traffic data:

a) A PC5 link identifier self-assigned to this PC5 unicast link; and

b) PQFI and its corresponding PC5 QoS parameters.

If the target UE accepts the PC5 unicast link setup request, the target UE may perform PC5 QoS flow setup over the PC5 unicast link as specified in clause 6.1.2.12.

6.1.2.2.4 completion of PC5 unicast link setup procedure by initiating UE

Upon receiving the direct link setup accept message, the initiating UE shall stop timer T5000, uniquely assign a PC5 link identifier and create a PC5 unicast link context for this PC5 unicast link. The target UE should then store the source layer 2ID and destination layer 2ID used in the transmission of this message provided by the lower layer in the PC5 unicast link context. From this time on, the initiating UE should use the established link for V2X communication over PC5 and additional PC5 signaling messages to the target UE.

After receiving the direct link setup accept message, the initiating UE should provide the following information to the lower layer along with the layer 2ID so that the lower layer can handle the incoming PC5 signaling or traffic data:

a) A PC5 link identifier self-assigned to this PC5 unicast link; and

b) PQFI and its corresponding PC5 QoS parameters.

In addition, the initiating UE may perform PC5 QoS flow establishment over the PC5 unicast link as specified in clause 6.1.2.12.

6.1.2.2.5 PC5 unicast link establishment procedure not accepted by target UE

If the direct link setup request message cannot be accepted, the target UE should send a direct link setup rejection message. The direct link setup rejection message contains a PC5 signaling protocol cause IE set to one of the following cause values:

#1 does not allow direct communication with the target UE;

#3 detects a collision of layer 2 IDs for unicast communication;

#5 lacks resources for the PC5 unicast link; or (b)

#111 protocol error, undefined.

If the target UE is not allowed to accept this request, e.g., based on operator policy or configuration parameters for V2X communication over PC5 as specified in clause 5.2.3, the target UE should send a direct link setup rejection message containing the PC5 signaling protocol cause value #1 "no direct communication to the target UE is allowed".

For a direct link setup request message received from a layer 2ID (for unicast communication), if the target UE already has an existing link established for a UE known to use this layer 2ID or is currently processing a direct link setup request message from the same layer 2ID, the target UE should send a direct link setup rejection message containing a PC5 signaling protocol cause value #3 "collision of layer 2ID detected for unicast communication".

If the PC5 unicast link establishment fails due to congestion problems, then the implementation specific maximum number of established NR PC5 unicast links has been reached, or other temporary lower layer problems causing resource constraints, then the target UE should send a direct link establishment rejection message containing the PC5 signaling protocol cause value #5 "lack resources for PC5 unicast link".

For other reasons that lead to link setup failure, the target UE should send a direct link setup rejection message containing the PC5 signaling protocol cause value #111 "undefined protocol error".

Upon receiving the direct link establishment rejection message, the initiating UE shall stop timer T5000 and abort the PC5 unicast link establishment procedure. If the PC5 signaling protocol cause value in the direct link setup reject message is either #1 "no direct communication with the target UE is allowed" or #5 "lack of resources for the PC5 unicast link", then the UE should not attempt to initiate a PC5 unicast link setup with the same target UE for at least the time period T.

Note that: the length of the time period T is UE implementation specific and may be different for the case when the UE receives the PC5 signaling protocol cause value #1 "no direct communication to the target UE is allowed" or when the UE receives the PC5 signaling protocol cause value #5 "lack of resources for the PC5 unicast link".

6.1.2.2.6 abnormality

6.1.2.2.6.1 initiated abnormal situation at UE

If timer T5000 expires, the initiating UE should retransmit the direct link setup request message and restart timer T5000. After the maximum number of allowed retransmissions is reached, the initiating UE should abort the PC5 unicast link setup procedure and may inform the upper layer that the target UE is not reachable.

And (3) injection: the maximum number of retransmissions allowed is UE implementation specific.

If the link no longer needs to be established before the procedure is completed, the initiating UE should abort the procedure.

6.1.2.2.6.2 abnormal situation at target UE

For a direct link setup request message received from a source layer 2ID (for unicast communication), if the target UE already has an existing link established for a UE known to use this source layer 2ID and the new request contains the same source user information as the known user, the UE shall process the new request. However, the target UE should delete the existing link context only after the new link setup procedure is successful.

[...]

6.1.2.6PC5 unicast link authentication procedure

6.1.2.6.1 general rule

The PC5 unicast link authentication procedure is used to perform mutual authentication of the UEs establishing the PC5 unicast link during the PC5 unicast link establishment procedure or the PC5 unicast link key update procedure, and derive a new K shared between the two UEs _NRP . After successful completion of the PC5 unicast link authentication procedure, the new K _NRP For secure establishment during the PC5 unicast link security mode control procedure as specified in clause 6.1.2.7. The UE that sends the direct link authentication request message is referred to as the "originating UE" and the other UE is referred to as the "target UE".

6.1.2.6.2 initiated by the PC5 unicast link authentication procedure by the initiating UE

The initiating UE should satisfy one of the following preconditions before initiating the PC5 unicast link authentication procedure:

a) The target UE has initiated the PC5 unicast link setup procedure towards the initiating UE by sending a direct link setup request message:

1) Direct link setup request message:

1) A target user information IE containing an application layer ID of the initiating UE; or (b)

2) Does not contain the target user information IE and the initiating UE is interested in the V2X service identified by the V2X service identifier in the direct link setup request message; and is also provided with

2)K _NRP The ID is not included in the direct link setup request message, or the initiating UE does not have K for inclusion in the direct link setup request message _NRP Existing K of ID _NRP Or initiate UE hopes to derive new K _NRP The method comprises the steps of carrying out a first treatment on the surface of the Or (b)

b) The target UE has initiated the PC5 unicast link key update procedure towards the initiating UE by sending a direct link key update request message, and the direct link request message includes a re-authentication indication.

To initiate the PC5 unicast link authentication procedure, the initiating UE should create a direct link authentication request message. In this message, the initiating UE:

a) Will contain a key establishment information container.

Note that: the key establishment information container is provided by an upper layer.

After generating the direct link authentication request message, the initiating UE passes this message to the lower layer for transmission, to the layer 2ID of the initiating UE for unicast communication, and to the layer 2ID of the target UE for unicast communication.

The initiating UE should start a timer T5aaa. The UE should not send a new direct link authentication request message to the same target UE when the timer T5aaa is running.

Fig. 6.1.2.6.2 entitled "PC5 unicast link authentication procedure" of [3GPP TS 24.587 V16.1.0 ] is reproduced as fig. 12]

6.1.2.6.3 PC5 unicast link authentication procedure accepted by target UE

After receiving the direct link authentication request message, if the target UE determines that the direct link authentication request message can be accepted, the target UE should create a direct link authentication response message. In this message, the target UE:

a) A key establishment information container should be included.

After generating the direct link authentication response message, the target UE passes this message to the lower layer for transmission, to the layer 2ID of the target UE for unicast communication, and to the layer 2ID of the initiating UE for unicast communication.

6.1.2.6.4 completion of PC5 unicast link authentication procedure by initiating UE

After receiving the direct link authentication response message, the initiating UE will stop the timer T5aaa.

Note that: initiating UE derives new K during PC5 unicast link authentication procedure _NRP Depending on the authentication method used.

6.1.2.6.5 PC5 unicast link authentication procedure not accepted by target UE

If the direct link authentication request message cannot be accepted, the target UE should create a direct link authentication rejection message. In this message, the target UE should contain a PC5 signaling protocol cause IE indicating one of the following cause values:

# a: authentication fails.

After generating the direct link authentication reject message, the target UE should pass this message to the lower layer for transmission along with the layer 2ID of the originating UE for unicast communication and the layer 2ID of the target UE for unicast communication.

The target UE should abort the procedure in progress triggering the initiation of the PC5 unicast link authentication procedure.

Upon receiving the direct link authentication reject message, the initiating UE should stop timer T5aaa and abort the procedure in progress triggering the initiation of the PC5 unicast link authentication procedure.

6.1.2.6.6 abnormality

6.1.2.6.6.1 initiated abnormal situation at UE

a) The timer T5aaa expires.

The initiating UE should retransmit the direct link authentication request message and restart the timer T5aaa. After the maximum number of allowed retransmissions is reached, the initiating UE should abort the PC5 unicast link authentication procedure and should abort the procedure in progress triggering the initiation of the PC5 unicast link authentication procedure.

b) This PC5 unicast link need not be used until the PC5 unicast link authentication procedure is completed.

The initiating UE should abort the procedure and should abort the procedure in progress triggering the initiation of the PC5 unicast link authentication procedure.

6.1.2.7PC5 unicast link security mode control program

6.1.2.7.1 general rule

The PC5 unicast link security mode control procedure is used to establish security between two UEs during the PC5 unicast link setup procedure or the PC5 unicast link key update procedure. After successful completion of the PC5 unicast link security mode control procedure, a security algorithm and key are selected for integrity protection and encryption of all PC5 signaling messages exchanged between UEs, and a security context may be used to protect all PC5 user plane data exchanged between UEs. The UE that sends the direct link security mode command message is referred to as the "initiating UE" and the other UE is referred to as the "target UE".

The editor annotates: whether the user plane is protected by a security association is to be studied further.

6.1.2.7.2 initiated by the PC5 unicast Link Security mode control procedure by the initiating UE

The initiating UE will meet the following precondition before initiating the PC5 unicast link security mode control procedure:

1) Direct link setup request message:

i) A target user information IE containing an application layer ID of the initiating UE; or (b)

ii) no target user information IE is contained and the initiating UE is interested in the V2X service identified by the V2X service identifier in the direct link setup request message; and is also provided with

2) The initiating UE has been based on K contained in the direct link setup request message _NRP ID identifies the existing K _NRP Or derive a new K _NRP The method comprises the steps of carrying out a first treatment on the surface of the Or (b)

b) The target UE has initiated the PC5 unicast link key update procedure towards the initiating UE by sending a direct link key update request message, and:

1) If the target UE has included a reauthentication indication in the direct link key update request message, then the initiating UE has derived a new K _NRP 。

If the initiating UE has derived a new K _NRP Then the initiating UE will generate K _NRP 16 MSBs of ID to ensure the resulting K _NRP The ID is unique in the initiating UE.

Next, the initiating UE will:

a) Generating a 128 bit nonce_2 value;

b) From K received in direct link setup request message _NRP Deriving K from Nonce_2 and Nonce_1 _NRP-sess For example 3GPP TS 33.536[yy]Is specified in (a);

c) From K _NRP-sess And the selected security algorithm derives an NR PC5 encryption key NRPEK and an NR PC5 integrity key NRPIK, e.g. 3GPP TS 33.536[yy ]Is specified in (a), and

d) A direct link security mode command message is created. In this message, the initiating UE:

1) If a new K has been derived at the initiating UE _NRP And is used for generating K _NRP The authentication method of (1) needs to send information to complete the authentication procedure, then a key establishment information container is included;

2) If a new K has been derived at the initiating UE _NRP Then will contain K _NRP MSB of ID;

3) Nonce_2, which will contain a 128-bit temporary value set to be generated by the initiating UE for the purpose of session key establishment over this PC5 unicast link;

4) Will contain the selected security algorithm;

5) The direct link establishment request message or the direct link key update request message contains the UE security capability received from the target UE; and is also provided with

6) Will contain K selected by the initiating UE _NPR-sess 8 LSBs of ID, e.g. 3GPP TS 33.536[yy]As specified in (a).

The editor annotates: if the PC5 unicast link security mode control procedure is triggered during the PC5 unicast link setup procedure, the initiating UE shall further investigate whether the UE PC5 unicast signaling security policy received from the target UE is contained in the direct link setup request message.

The initiating UE will update the request message according to the K received in the direct link establishment request message or the direct link key _NPR-sess 8 MSBs of ID and K contained in direct link security mode command message _NPR-sess The 8 LSBs of the ID form K _NPR-sess ID。

The initiating UE will not encrypt the direct link security mode command message, but will integrity protect it with the new security context.

After generating the direct link security mode command message, the initiating UE should pass this message to the lower layer for transmission along with the layer 2ID of the initiating UE for unicast communication and the layer 2ID of the target UE for unicast communication, and start timer T5bbb. The UE should not send a new direct link security mode command message to the same target UE when the timer T5bbb is in operation.

Fig. 6.1.2.7.2 entitled "PC5 unicast link security mode control program" of [3GPP TS 24.587 V16.1.0 ] is reproduced as fig. 13]

6.1.2.7.3 PC5 unicast Link Security mode control procedure accepted by target UE

After receiving the direct link security mode command message, if the PC5 unicast link security mode control procedure is triggered during the PC5 unicast link setup procedure, the target UE will verify the K contained in the direct link security mode command message _NPR-sess The 8 LSBs of the ID are not set to be associated with a direct link establishment request message from another UE in response to the target UE The received values are the same value.

Next, the target UE will:

a) K received from direct link security mode command message _NRP Deriving K from Nonce_1 and Nonce_2 _NRP-sess For example 3GPP TS 33.536[yy]Is specified in (a); and

b) From K _NRP-sess And the selected security algorithm derives NRPEK and NRPIK, e.g. 3GPP TS 33.536[yy]As specified in (a).

The target UE will determine whether the direct link security mode command message can be accepted by:

a) Checking the integrity of the direct link security mode command message using NRPIK; and

b) The received UE security capability is checked as not changed compared to the value the target UE sent to the initiating UE in the direct link setup request message or the direct link key update request message.

The editor annotates: whether the target UE needs to perform a check related to the UE signaling security policy is to be further investigated.

If the target UE does not include K in the direct link setup request message _NRP ID, then the target UE includes a reauthentication indication in the direct link key update request message, or initiates UE selection to derive a new K _NRP Target UE should be as 3GPP TS 33.536[yy]Is regulated to export K _NRP . The target UE should select K _NRP 16 LSBs of ID to ensure the resulting K _NRP The ID will be unique in the target UE. The target UE shall receive K _NRP MSB of ID and K selected by the same _NRP LSB of ID forms K _NRP ID, and should be in contact with K _NRP Storing the complete K together _NRP ID。

If the target UE accepts the direct link security mode command message, the target UE should create a direct link security mode complete message. In this message, the target UE:

a) Shall contain PQFI and corresponding PC5 QoS parameters;

b) If IP communication is used, an IP address configuration IE set to one of the following values should be included:

1) "IPv6 router" if the target UE only supports IPv6 address allocation mechanism, i.e., acts as an IPv6 router; or (b)

c) If IP communication is used and the IP address configuration IE is set to "IPv6 address allocation is not supported," then a link local IPv6 address IE formed locally based on IETF RFC 4862[6] will be included; and

d) If a new K is derived _NRP Then will contain K _NRP 16 LSBs of the ID.

The editor annotates: whether the target UE includes its UE PC5 unicast user plane security policy in the direct link security mode completion is to be further investigated.

The target UE will update the K that it has sent in the direct link setup request message or the direct link key according to _NPR-sess 8 MSBs of ID and K received in direct link security mode command message _NPR-sess 8 LSBs of ID to form K _NPR-sess ID。

The target UE will encrypt and integrity protect the direct link security mode complete message with the new security context.

After generating the direct link security mode complete message, the target UE should pass this message to the lower layer for transmission along with the layer 2ID of the target UE for unicast communication and the layer 2ID of the initiating UE for unicast communication.

6.1.2.7.4 is completed by the PC5 unicast link security mode control procedure by the initiating UE

After receiving the direct link security mode complete message, the initiating UE should stop timer T5bbb and check the integrity of the direct link security mode complete message. If the integrity check passes, the initiating UE should then continue to trigger the procedure of the PC5 unicast link security mode control procedure.

6.1.2.7.5 PC5 unicast Link Security mode control procedure not accepted by target UE

If the direct link security mode command message is not acceptable, the target UE should send a direct link security mode rejection message and abort the procedure in progress triggering initiation of the PC5 unicast link security mode control procedure. The direct link security mode rejection message contains a PC5 signaling protocol cause IE indicating one of the following cause values:

# a: authentication fails;

# b: integrity failure;

#c: UE security capability mismatch;

#d：K _NPR-sess LSB collision of ID; or (b)

#111: protocol error, undefined.

The editor annotates: whether a PC5 signaling protocol cause value for UE PC5 unicast signaling security policy mismatch is needed is to be further investigated.

After receiving the direct link security mode rejection message, the initiating UE should stop timer T5bbb and:

a) If the PC5 signaling protocol cause IE in the direct link security mode rejection message is set to #e, then it is used for K _NPR-sess Retransmitting the direct link security mode command message by a different value of 8 LSBs of the ID; and

b) Otherwise, the program in progress triggering the initiation of the PC5 unicast link security mode control program is aborted.

6.1.2.7.6 abnormality

6.1.2.7.6.1 initiated abnormal situation at UE

a) Timer T5bbb expires.

The initiating UE should retransmit the direct link security mode command message and restart the timer T5bbb. After the maximum number of allowed retransmissions is reached, the initiating UE should abort the PC5 unicast link security mode control procedure and should abort the procedure in progress triggering the initiation of the PC5 unicast link security mode control procedure.

Note that: the maximum number of retransmissions allowed is UE implementation specific.

b) The use of this PC5 unicast link is no longer required before the PC5 unicast link security mode control procedure is completed.

The initiating UE should abort the procedure and should abort the procedure in progress triggering the initiation of the PC5 unicast link security mode control procedure.

[...]

7.3.2 direct Link establishment acceptance

7.3.2.1 message definition

This message is sent by the UE to another peer UE to accept the received direct link setup request message. See table 7.3.2.1.1.

Message type: direct link establishment acceptance

Importance: dual-purpose

The direction is: UE to peer UE

[ Table 7.3.2.1.1 titled "direct Link establishment accepted message content" of 3GPP TS 24.587 V16.1.0 is reproduced as FIG. 14]

[...]

7.3.14 direct link security mode completion

7.3.14.1 message definition

This message is sent by the UE to another peer UE in response to the direct link security mode command message. See table 7.3.14.1.1.

Message type: direct link security mode completion

Importance: dual-purpose

The direction is: UE to peer UE

Table 7.3.14.1.1 entitled "D direct Link Security mode completion message content" of 3GPP TS 24.587 V16.1.0 is reproduced as FIG. 15

3GPP TR 23.752 describes the following:

5.3 key issue #3: support for UE to network relay

5.3.1 general description

From TS 22.261[3] and TS 22.278[2], support for UE to network relay needs to be studied. In addition, rel-16 5G architecture design (e.g., flow-based QoS communication over the PC5/Uu interface) should also be considered.

Consider the case where the UE shown in fig. 5.3.1-1 may be able to access the network via direct network communication or indirect network communication, where path #1 is a direct network communication path that may not exist, and path #2 and path #3 are indirect network communication paths to the network repeater via different UEs.

Fig. 5.3.1-1 entitled "example context of direct or indirect network communication path between UE and network" of 3GPP TR 23.752 V0.5.0 is reproduced as fig. 16

Thus, 5G ProSe needs to support UE-to-network relay. In particular, the following aspects need to be studied:

how to authorize the UE to access the 5GC for 5G UE-to-network relay and how to authorize the UE to access the 5GC via 5G UE-to-network relay.

How to establish a connection between a remote UE and a UE-to-network relay to support connectivity to the network for the remote UE.

How to support end-to-end requirements between remote UE and network via UE-to-network relay, including handling of QoS (e.g. data rate, reliability, latency) and PDU session related attributes (e.g. S-NSSAI, DNN, PDU session type and SSC mode).

How the network allows and controls QoS requirements for 5G ProSe UE to NW relay.

How to transfer data between a remote UE and the network through UE-to-network relay.

Note 1: security and privacy aspects will be handled by the savg g 3.

How to (re) select UE-to-network relay for communication path selection between two indirect network communication paths (i.e. path #2 and path #3 in fig. 5.3.1-1).

How to perform communication path selection between a direct network communication path (i.e., path #1 in fig. 5.3.1-1) and an indirect network communication path (i.e., path #2 or path #3 in fig. 5.3.1-1).

How to guarantee service continuity during these communication path switching procedures for switching between a direct network communication path and an indirect communication path and for switching between two indirect network communication paths.

And (2) injection: support for non-unicast mode communications (i.e., one-to-many communications/broadcast or multicast) between the network and the UE-to-network relay UE and between the UE-to-network relay and the remote UE depends on the outcome of fs_5mbs operation.

Two cases may be considered with respect to support for UE-to-network relay, i.e., UE-to-network relay served by the gNB as shown in fig. 5.3.1-2 and UE-to-network relay served by the ng-eNB as shown in fig. 5.3.1-3.

Fig. 5.3.1-2 entitled "UE-to-network relay served by gNB" of 3GPP TR 23.752 V0.5.0 is reproduced as fig. 17]

Fig. 5.3.1-3 entitled "UE-to-network relay served by ng-eNB" of 3GPP TR 23.752 V0.5.0 is reproduced as fig. 18]

And (3) injection: whether or not the UE-to-network relay is supported is served by the ng-eNB depends on the solution to be identified in the present study and RAN decisions.

And (4) injection: proSe UE-to-network relay based on LTE PC5 may be supported when the UE-to-network relay moves to E-UTRAN, as defined in TS 23.303[9] for public safety.

[...]

6.6 solution #6: layer 3UE to network relay

6.6.1 description

This is a solution for the key problem #3UE to network relay.

ProSe 5G UE-to-network relay entity provides functionality for remote UEs to support connectivity to the network (see fig. 6.6.1-1). Which may be used for public safety services and business services (e.g., interactive services).

The UE is considered a remote UE for a ProSe UE-to-network relay provided that it has successfully established a PC5 link to this ProSe 5G UE-to-network relay. The remote UE may be located within NG-RAN coverage or outside NG-RAN coverage.

The remote UE may perform communication path selection between the direct Uu path and the indirect Uu path based on the link quality and a configured threshold (either pre-configured or provided by the NG-RAN). For example, if Uu link quality exceeds a configured threshold, then a direct Uu path is selected. Otherwise, an indirect Uu path is selected by performing UE-to-network relay discovery and selection.

[ FIG. 6.6.1-1 entitled "architecture model Using ProSe 5G UE to network Relay" of 3GPP TR 23.752 V0.5.0 is reproduced as FIG. 19]

ProSe 5G UE-to-network relay should relay unicast traffic (UL and DL) between the remote UE and the network. ProSe UE-to-network relay should provide generic functionality that can relay any IP, ethernet, or unstructured traffic;

ProSe UE-to-network relay uses IP type PDU sessions towards 5GC for IP traffic on PC5 reference point.

For ethernet traffic on the PC5 reference point, proSe UE-to-network relay may use an ethernet type PDU session or an IP type PDU session towards 5 GC.

ProSe UE-to-network relay may use unstructured type PDU sessions or IP type PDU sessions towards 5GC for unstructured traffic on PC5 reference point (i.e. IP encapsulation/decapsulation by UE-to-network relay).

The type of traffic supported on the PC5 reference point is indicated by ProSe UE to network relay, e.g. using a corresponding relay service code. The UE-to-network relay determines the PDU session type based on, for example, proSe policies/parameters, urs rules, relay service codes, etc.

Note that: how the UE to NW relay determines the PDU session type should be evaluated independently of the other parts of this solution while taking into account other PDU session parameters, e.g. DNN, SSC mode.

IP type PDU sessions and ethernet type PDU sessions may be used to support more than one remote UE, while unstructured type PDU sessions may be used to support only one remote UE.

The editor annotates: support for non-unicast mode communications (i.e., one-to-many communications/broadcast or multicast) between the network and the UE-to-network relay UE and between the UE-to-network relay and the remote UE depends on the outcome of fs_5mbs operation.

One-to-one direct communication is used between the remote UE and ProSe 5G UE to network repeater for unicast traffic as specified in the solution for critical issue # 2.

The protocol stack for layer 3UE to network repeater is shown in fig. 6.6.1-2.

Fig. 6.6.1-2 entitled "protocol stack for ProSe 5G UE to network relay" of 3GPP TR 23.752 V0.5.0 is reproduced as fig. 20]

Hop-by-hop security is supported in the PC5 link and Uu link. Security on the application PDU layer is required if there is a requirement beyond hop-by-hop security for protecting the traffic of the remote UE.

Further security details (integrity and privacy protection for remote UE-Nw communications) will be specified in the savg 3.

From the definition of service continuity in TS 22.261[3] and TS 23.501[6], it can be seen that "service continuity" differs from "session continuity" by definition, and that service continuity can be implemented at the application layer regardless of IP address reservation:

For mission critical services in public safety, service continuity may be achieved through an application layer mechanism, as described for example in annex B in TS 23.280[29 ].

For commercial IMS use cases, service continuity may be achieved using the mechanism described in TS 23.237[30 ].

Service continuity, e.g. QUIC, can be implemented in a similar way for commercial use cases with application layers that deviate from the 3GPP range (e.g. non-IMS).

It should be noted that all of the above described application layer mechanisms can be reused in layer 3 UEs into the network and thus no enhancements are required in the present study item.

6.6.2 procedure

A ProSe 5G UE-to-network relay capable UE may register with the network (if not already registered) and establish a PDU session that implements the necessary relay service, or it may need to connect to an additional PDU session or modify an existing PDU session in order to provide relay service towards a remote UE. The PDU session supporting UE-to-network relay should be used only for remote ProSe UE relay traffic.

Fig. 6.6.2-1 entitled "ProSe 5G UE to network relay" of [3GPP TR 23.752 V0.5.0 ] is reproduced as fig. 21]

0. During the registration procedure, authorization and provisioning is performed for ProSe UE to NW relay (0 a) and remote UE (0 b). The authorization and provisioning procedure may be any solution for the critical questions #1 and # 3.

Prose 5g UE-to-network relay may establish a PDU session, e.g., S-NSSAI, DNN, SSC mode or PDU session type, for relaying with default PDU session parameters received in step 0 or preconfigured in the UE-to-NW relay. In the case of IP PDU session type and IPv6, proSe UE-to-network relay obtains the IPv6 prefix from the network via a prefix delegation function, as defined in TS 23.501[6 ].

2. Based on the authorization and provisioning in step 0, the remote UE performs discovery of ProSe 5G UE to network relay using any solution to critical issues #1 and # 3. As part of the discovery procedure, the remote UE knows the connectivity services provided by ProSe UE to network relay.

3. The remote UE selects ProSe 5G UE to network relay and establishes a connection for one-to-one ProSe direct communication as described in TS 23.287[5 ].

If there is no PDU session, e.g., S-NSSAI, DNN, qoS, that meets the requirements of the PC5 connection with the remote UE, then the ProSe 5G UE-to-network relay initiates a new PDU session establishment or modification procedure for relaying.

ProSe 5G UE-to-network relay performs relay functions at the corresponding layer according to the PDU session type for relay, e.g. acts as an IP router when the traffic type is IP, as an ethernet switch when the traffic type is ethernet, and performs generic forwarding for unstructured traffic.

When ProSe 5G UE-to-network relay uses unstructured PDU session type for unstructured traffic on the PC5 reference point, it creates a mapping between PC5 link identifier and PDU session ID, and a mapping between PFI for PC 5L 2 link and QFI for PDU session.

When ProSe 5G UE-to-network relay uses IP PDU session type for unstructured traffic on ethernet or PC5 reference point, it locally assigns IP address/prefix for remote UE and uses it to encapsulate data from remote UE. For downlink traffic, proSe 5G UE-to-network relay decapsulates traffic from the IP header and forwards to the corresponding remote UE via the PC5 reference point.

The editor annotates: the requirements of how ProSe UE to NW relay determines PC5 connections will be specified in other solutions for KI #3, e.g. S-NSSAI, DNN, qoS.

The editor annotates: in other solutions, it is addressed how to support the end-to-end QoS requirements of the remote UE, including QoS enforcement for PC5 and PDU sessions for relay.

4. For IP PDU session type and IP traffic on the PC5 reference point, an IPv6 prefix or IPv4 address is assigned for the remote UE as defined in TS 23.303[9] clauses 5.4.4.2 and 5.4.4.3. Thus, uplink and downlink relay may begin. For downlink traffic forwarding, the PC5 QoS rules are used to map downlink IP packets to PC5 QoS flows. For uplink traffic forwarding, 5G QoS rules are used to map uplink IP packets to Uu QoS flows.

The editor annotates: the general functionality for IPv6 prefix delegation as defined in clause 5.3.1.2.6 of TS 23.401[25] requires that a reference to TS 23.501[6] be added in 5GS and above.

Prose 5g UE-to-network relay sends a remote UE report (remote user ID, remote UE information) message to the SMF for PDU sessions associated with the relay. The remote user ID is the identity of the remote UE user that was successfully connected in step 3 (provided via user information). The remote UE information is used to assist in identifying the remote UE in the 5 GC. For IP PDU session types, the remote UE information is remote UE IP information. For the Ethernet PDU session type, the remote UE information is a remote UE MAC address detected by the UE-to-network relay. For unstructured PDU session types, the remote UE information contains a PDU session ID. The SMF stores the remote user ID and related remote UE information (if available) in the SM context of ProSe 5G UE-to-network relay for this relay-associated PDU session.

For IP information, the following principle applies:

for IPv4, the UE-to-network relay shall report the TCP/UDP port range assigned to the individual remote UE (along with the remote user ID);

for IPv6, the UE-to-network relay should report the IPv6 prefix assigned to the individual remote UE (along with the remote user ID).

The editor annotates: privacy protection for remote user IDs depends on the SA WG3 design.

When the remote UE disconnects from the ProSe 5G UE to the network relay (e.g., after explicit layer 2 link release or based on keep-alive messages not existing on PC 5), a remote UE report message should be sent to inform the SMF that the remote UE has left.

In the case of a registration update procedure involving SMF changes, the remote user ID and related remote UE information corresponding to the connected remote UE is transferred to the new SMF as part of SM context transfer for ProSe 5G UE to network relay.

Note 1: in order for the SMF to have remote UE information, proSe 5G UE-to-network relay authorized operating HPLMN and VPLMN need to support transfer of remote UE related parameters if the SMF is in the HPLMN.

And (2) injection: when the remote UE disconnects from the ProSe UE to the network relay, the implementation decides how the ProSe 5G UE to the network relay clears/disconnects the relay PDU session.

After connecting to the ProSe 5G UE-to-network relay, the remote UE keeps performing measurements of the signal strength of the PC5 unicast link with the ProSe 5G UE-to-network relay for relay reselection.

The solution may also work when ProSe 5G UE-to-network relay UE is connected in EPS using LTE. In this case for remote UE reporting, the procedure defined in TS 23.303[9] may be used.

The editor annotates: how to perform rate limiting for remote UEs is to be studied further.

6.6.3 impact on services, entities and interfaces

The solution has an impact in the following entities:

SMF:

support of procedures for remote UE reporting is required.

UE：

Support procedures for remote UE and ProSe 5G UE to network relay are required.

[...]

6.23 solution #23: end-to-end security and IP address reservation for layer 3 UE-to-network relay using N3IWF

6.23.1 general description

This is a solution to support end-to-end security for remote UE traffic transmitted using layer 3 UE-to-network relay. Which may be used for public safety services and business services (e.g., interactive services). The solution is optional and complementary to the baseline layer 3 UE-to-network relay solution, e.g., as described in clause 6.6. Which may be used by remote UEs for services requiring end-to-end traffic confidentiality and/or IP address preservation.

To provide end-to-end security for remote UE traffic, the design of "untrusted non-3 GPP access to 5GC via N3 IWF" in clause 4.2.8 of TS 23.501[6] or "access to PLMN services via separate non-public networks" in clause 5.30.2.7 of TS 23.501[6] is utilized. The remote UE follows the procedure defined in TS 23.502[8] clause 4.12 to register with the 5GC via the N3IWF and establish the corresponding PDU session. Data traffic on the PDU session is IPSec protected between the remote UE and the N3 IWF.

To provide IP address reservation, the remote UE follows the procedure specified in TS 23.502[8] clause 4.9.2 (handover of PDU session procedure between 3GPP and untrusted non-3 GPP access) as the UE moves between direct network communication and indirect communication paths.

The N3IWF provides NAS connectivity to the 5GC and end-to-end security for remote UEs via UE-to-NW relay access (see figure 6.23.1-1). The N3IWF treats the remote UE as any N3GPP UE, i.e. there is no impact on the N3IWF.

The remote UE supports the PC5 procedure as defined in solution #6 in clause 6.6 for obtaining UE-to-NW relay access.

Fig. 6.23.1-1 entitled "non-roaming architecture model with UE to NW relay access using N3 IWF" of 3GPP TR 23.752 V0.5.0 is reproduced as fig. 22]

Since this solution is optional, not all UE-to-network relays provide PDU sessions to access the N3IWF.

The editor annotates: there is a need to define criteria and policies that are used by remote UEs to decide between secure N3 IWFs or others.

The editor annotates: there is a need to define criteria and policies that are used by the UE to network relay to provide secure N3IWF access or other.

The UE selection of the N3IWF follows regulatory rules of the country in which it is located, and the remote UE selects only the N3IWF within the local country when regulatory requirements require. QoS differentiation may be provided on a per IPsec child security association basis. N3IWF determines the IPsec progeny SA as defined in TS 23.502[8] clause 4.12. The N3IWF is preconfigured to assign different IPsec child SAs for QoS flows with different QoS profiles.

And (3) injection: in case the remote UE and the relay UE have registered to different PLMNs, e.g. when the Relay Service Code (RSC) has been configured, an SLA needs to be established to govern QoS treatment. The SLA may include a mapping between DSCP marking and N3IWF IP address for IPsec child SAs with remote UEs and corresponding QoS. The no change of DSCP field between the N3IWF and the UPF of the relay UE is also assumed to be governed by the SLA and by a transport level arrangement outside the 3GPP range. The packet detection filter at the UPF of the relay UE may be based on the N3IWF IP address and DSCP marking.

The 5GC registered by the UE-to-network relay and the 5GC registered by the remote UE may be the same or different. The solution does not force the remote UE to be served by the same PLMN as the relay UE.

6.23.2 protocol stack

When using access to the N3IWF, proSe 5G UE-to-network relay should be able to relay control plane (NAS) and user plane unicast traffic (UL and DL) between the remote UE and the network towards the N3 IWF. One-to-one direct communication is used between the remote UE and ProSe 5G UE to network repeater for unicast traffic as specified in the solution for critical issue # 2.

The remote UE and 5GC reuse the procedure defined in clause 4.12 of TS 23.502[8] for supporting registration and connection management from remote UE to 5GC through 5G ProSe UE to NW relay access. The remote UE establishes a signaling IPsec tunnel with the N3IWF through UE-to-NW relay access using an IKE procedure. Also, similar to the untrusted non-3 GPP access, subsequent NAS messages between the UE and the N3IWF are exchanged via signaling IPsec SA over TCP/IP. The control plane protocol stack before establishing the IPSec tunnel and after setting up the IPSec tunnel is the same as the untrusted non-3 GPP access protocol stack and is shown in fig. 6.23.2-2. In (a)

Fig. 6.23.2-2 entitled "control plane protocol stack between remote UE and N3IWF for L3 UE to NW relay access" of 3GPP TR 23.752 V0.5.0 is reproduced as fig. 23

The remote UE supports NAS MM (after registration), SMS and PDU session setup/modification/release procedures for 5GC of remote UE traffic by transporting corresponding NAS signaling over a signaling IPsec tunnel established with the N3 IWF.

The remote UE transmits/receives UP traffic over the PC5 UE-to-NW relay path via the child IPSec SA tunnel to the N3IWF through the relayed PDU session established for the remote UE traffic. The PCF may provide corresponding urs rules to assist the remote UE in identifying the services that need to access the N3 IWF. In deployment, the UPF and the N3IWF of the relay UE may be collocated.

The user plane protocol stack for L3 UE to NW relay access via N3IWF is the same as for untrusted non-3 GPP access and is shown in fig. 6.23.2-3. The type of PDU session used between the relay UE and the relay UE UPF is IP, whereas traffic transported in the PDU layer (PDU session anchor) between the remote UE and the UPF may be IP, ethernet or unstructured.

Fig. 6.23.2-3 entitled "user plane protocol stack between remote UE and N3IWF for L3 UE to NW relay access" of [3GPP TR 23.752 V0.5.0 ] is reproduced as fig. 24]

The solution is transparent to the NG-RAN. The NG-RAN (gNB) does not have any different processing for traffic of the remote UE to be compared with traffic in the baseline layer 3 UE-to-network relay solution described in e.g. clause 6.6.

The editor annotates: in terms of the overhead introduced by the N3IWF access and L3 IP relay over the radio interface (especially on PC 5), whether there is a potential impact from this solution should be assessed by the RAN WG (at least in terms of radio efficiency, latency and reliability).

The editor annotates: how the remote UE will impose and enforce mobility restrictions is to be studied further

6.23.3 procedure

6.23.3.1 remote UE 5GC registration accessed through L3 UE to NW relay

The 5G ProSe UE-to-network relay capable of accessing the N3IWF may register with the network (if not already registered) and establish a PDU session to implement the necessary relay services to the N3 IWF. The 5G ProSe UE to NW relay may need to connect to additional PDU sessions or modify existing PDU sessions in order to provide relay services towards the remote UE.

Alternatively, if different treatments, e.g. priorities, are required, proSe UE to NW relay may use two different PDU sessions, one for NAS traffic of the remote UE and the other for UP traffic of the remote UE via N3 IWF.

Fig. 6.23.3-1 entitled "remote UE 5GC registration through L3 UE to NW relay access" of [3GPP TR 23.752 V0.5.0 ] is reproduced as fig. 25]

The 1 remote UE and 5G ProSe UE to NW relay may perform a registration procedure and obtain ProSe policy and urs policy information when in coverage. ProSe policy and urs policy indicate whether a remote UE should access 5GC via N3IWF to get a specific service or service flow (indicated by urs). The authorization and provisioning procedure may be any solution for the critical questions #1 and # 3.

The remote UE that must be out of box and ready to use will be preconfigured with ProSe policy and urs policy information.

Prose UE to NW relay and remote UE follow the procedure described in steps 1-4 in clause 6.6.2 procedure of solution # 6: layer 3UE to network relay with the following enhancements for N3IWF support:

remote UE and ProSe UE-to-network relay are configured (via provisioning or pre-configuration) with a specific relay service code.

Note that: services requiring access via the N3IWF may be configured with RSCs that may be served by the same relay.

5. The remote UE selects an N3IWF and determines an N3IWF IP address.

The editor annotates: the remote UE N3IWF selection procedure is to be further investigated. It may follow the N3IWF selection procedure defined in clause 6.3.6.2 of TS 23.501[6] for untrusted non-3 GPP access as a baseline, but may require modification.

6. The remote UE establishes a signaling IPsec tunnel using an IKE procedure with an N3IWF and performs NAS registration as shown in figure 4.12.2.2-1 of TS23.502[8 ]. After establishing the IPSec tunnel, the remote UE may perform any of the NAS procedures (including PDU session establishment for the relay PDU session) as specified in clause 4.12 of TS23.502[8 ].

IKE keep-alive between the remote UE and the N3IWF is used to detect possible path failures. When the remote UE and the N3IWF support MOBIKE, the remote UE may change the relay UE while maintaining the session with the N3 IWF. This is negotiated between the remote UE and the N3IWF as specified in TS23.502[8] clause 4.12.2.2. When IKE keep-alive is used, the remote UE needs to keep PC5 connected and the relay UE keeps PDU session.

6.23.3.2 UE movement between direct network communication and indirect communication paths

Clause TS23.502[8] clause 4.9.2.2 applies after the remote UE establishes a PC5 connection to the relay UE when the UE moves from direct network communication to an indirect communication path.

When the UE moves from an indirect communication path to direct network communication, the UE complies with clause TS23.502[8] clause 4.9.2.1.

6.23.4 impact on services, entities and interfaces

The solution has an impact in the following entities:

5GC entity (AMF, PCF, UPF):

it is necessary to support non-3 GPP access via N3IWF, as defined in TS 23.501[6] and TS 23.502[8 ].

NG-RAN：

-functionality regarding the solution adopted for QoS treatment.

N3IWF：

-none.

Relay UE:

configured to establish a PDU session for relay (network configuration ensures that this PDU session provides access to the N3 IWF).

Remote UE:

the remote UE needs to support at least running the Rel-15 defined procedure for untrusted non-3 GPP access through the N3IWF through the L3 UE to NW relay.

6.24 solution #24: end-to-end QoS support for layer 3 UE-to-network relay

6.24.1 general description

This solution solves the key problem #3 "support of ue to network relay". In particular, this solution addresses aspects of how to support end-to-end requirements between remote UE and network via UE-to-network relay, including QoS (e.g., data rate, reliability, latency) and how the network allows and controls QoS requirements for 5G ProSe UE-to-NW relay.

In the layer 3UE to NW relay solution (solution # 6), the data flow of the remote UE is served by the PDU session of the relay UE. Since the UE-to-network relay path includes two branches (PC 5 and Uu) as shown in the following diagram 6.24.1-1, the end-to-end QoS can be satisfied only when the QoS requirements are properly divided and respectively satisfied on the two branches.

Fig. 6.24.1-1 entitled "end-to-end QoS partitioning for layer 3 UE-to-network relay solution" of 3GPP TR 23.752 V0.5.0 is reproduced as fig. 26]

The QoS requirements for the PC5 LINK are controlled by PC5 QoS rules and PC5 QoS parameters (PQI, GFBR, MFBR, PC LINK-AMBR, range, etc.), as specified in clause 5.4 of TS 23.287[5 ]. The QoS requirements for Uu links are controlled via 5G QoS rules and 5G QoS parameters (5 QI, GFBR, MFBR, etc.), as specified in clause 5.7 of TS 23.501[6 ].

The QoS of the Uu leg is associated with the PDU session established by the UE to network relay and therefore the procedure as defined in TS 23.502[8] clauses 4.3.2 and 4.3.3 applies. The SMF of the UE-to-network relay will provide the corresponding QoS rules and flow layer level QoS parameters to the UE-to-network relay.

As explained above, UE-to-network relay needs to translate Uu QoS information into corresponding PC5 QoS parameters in order to achieve proper end-to-end QoS. Since remote UEs and UE-to-network relays use the PC5 unicast communication mode, most of the flow-level QoS parameters can be directly reused. The only parameters that need assistance in the conversion are the mapping of 5QI and PQI. The UE-to-network relay must be configured with appropriate mapping information. The mapping of 5QI and PQI is configured at the UE-to-network relay for a particular service or group for a service. The 5QI for Uu is used with the PQI for PC5 to support end-to-end QoS requirements.

Note 1: the service or group of services may be identified by a relay service code, IP 3 tuple, or the like.

In the case where QoS flow setup is network initiated, the PCF or SMF decides Uu part QoS parameters. Based on this information received from the SMF, the UE-to-network relay uses the procedure defined in TS 23.287[5] clause 6.3.3.4 to infer PC5 partial QoS parameters and establish the corresponding PC5 QoS flows. For example, after receiving the QoS rules and the flow layer level parameters, the relay UE determines the corresponding PC5 QoS flows to be established and the mapping between Uu QoS flows and PC5 QoS flows.

In the case where the remote UE requests a dedicated PC5 QoS flow when an L2 link is established through PC5, the remote UE decides on the PC5 part QoS parameters, the UE-to-network may map the PC5 QoS requirements into Uu QoS requirements, and perform the UE-requested PDU session modification as defined in TS 23.502[8] clause 4.3.3.

6.24.2 enhancement to support dynamic QoS treatment

AS shown in fig. 6.24.1-1, the end-to-end connection from the remote UE to the AS involves two air links, uu and PC5. Thus, in order to meet the PDB for a particular service, the AN PDB utilized by the NG-RAN needs to be reduced in order to give some budget for the PC5 link. It should be noted that this is independent of whether an L2 or L3 relay architecture is used.

One way to achieve this without affecting the NG-RAN is for the SMF to modify the PDB signaled to the NG-RAN in the QoS profile of the QoS flow for the traffic of the remote UE. SMF follows PCC rules (if it is PCF determination) or deducts PDB based on local configuration.

When dynamic PCC control is supported, the SMF may determine the PDB to use based on PCC rules. Otherwise, the SMF may use DNN and/or S-NSSAI to determine whether and how to modify the PDB based on the pre-configuration, for example.

When supporting dynamic PCC control, it is possible that the AF may be able to request some QoS treatment of the traffic when the remote UE initiates the session. This may be achieved by using the features as defined in clause 6.1.3.22 of TS 23.503[18 ]. The AF can locate the UE to network relayed PCF using the procedure as defined in TS 23.503[18] clause 6.1.1.2 because the remote UE uses the address of the PDU session belonging to the UE to network relay.

The PCF may determine Uu part QoS parameters and generate corresponding PCC rules, and the SMF in turn generates QoS rules and flow layer level QoS parameters and signals the UE to the network relay using PDU session modification procedure. The UE-to-network relay then infers PC5 part QoS parameters based on the configured mappings of 5QI and PQI and sets up the relevant PC5 QoS flows using the L2 link modification procedure defined in TS 23.287[5] clause 6.3.3.4.

And (3) injection: since the UE-to-network relay uses the configured mapping of 5QI and PQI to derive PC5 part QoS parameters, the end-to-end QoS requirements provided by the AF that cannot be aligned with the configured mapping of 5QI and PQI are not supported in this solution.

In the case of using the network scheduling operation mode for NR PC5, the procedure defined in TS 23.287[5] clause 5.4.1.4 is used to authorize the PC5 QoS request related to the relay operation.

The editor annotates: how to determine QoS parameters for PDU sessions is to be further investigated, e.g. which UE subscription to use.

Alternatively, dynamic QoS handling for remote UEs may be controlled using reflected QoS through Uu as defined in TS23.502[8] clause 5.7.3.5. In particular, it does not require any explicit intervention from the SMF. This may potentially save signaling between the SMF and the UE-to-network relay UE for frequently modifying the relay PDU session on Uu.

Upon receiving a DL packet with an RQI on Uu for a remote UE, the UE-to-network relay may optionally derive QoS rules corresponding to the remote UE based on the indicated QFI. The derived rule is for UL packets from the remote UE that will use the new QFI (RQoS based).

To do so, the UE-to-network relay may determine the PQI based on the indicated 5QI (due to reflected QoS) on DL Uu. The UE-to-network relay may locally associate the remote UE (i.e., with the remote UE's PC5 QoS flows) to the derived QoS rules.

The UE-to-network relay may then modify the mapping between the associated PC5 QoS flows or Uu and the PC5 QoS flows towards the remote UE in order to match the PQI of the PC5 flows to the indicated 5QI on DL Uu. The UE-to-network relay then modifies the relevant PC5 QoS flows using, for example, the L2 link modification procedure as defined in TS 23.287[5] clause 6.3.3.4.

When the UE-to-network relay deletes the derived QoS rule, e.g., after expiration of the RQ timer, the UE-to-network relay resumes using the transmitted QoS rule and accordingly executes the L2 link modification procedure defined in TS 23.287[5] clause 6.3.3.4 to use the PQI of 5QI corresponding to the existing transmitted QoS rule.

The editor annotates: how to activate the reflected QoS control for UE to network relay is yet to be further investigated.

The editor annotates: whether UE-to-network relay needs to modify the mapping between Uu and PC5 QoS flows based on DL packets with RQI is to be studied further.

6.24.2 procedure

Existing procedures defined in TS 23.502[8] and TS 23.287[5] can be used to manage QoS flows and PC5 QoS flows to serve remote UEs.

6.24.3 impact on services, entities and interfaces

The solution has an impact in the following entities:

SMF：

the SMF optionally supports modifying the PDB for QoS flows serving the remote UE based on PCC rules or pre-configuration.

UE：

-5G ProSe UE-to-network relay comprising a mapping of 5QI to PQI based on configuration supporting Uu flow level QoS parameters to PC5 QoS parameters.

-the 5G ProSe UE-to-network relay modifying the PQI of the PC5 link to match the QFI of the derived QoS rules.

Remote UE support deciding PC5 part QoS parameters based on E2E QoS parameters.

PCF：

Support for deciding Uu part QoS parameters based on E2E QoS parameters.

6.25 solution #25: qoS handling for layer 3UE to network relay

6.25.1 description

This is a solution for the key problem #3UE to network relay. In particular it is used for QoS control of layer 3UE to network relay.

For a remote UE accessing a network via UE-to-network relay, qoS control between the remote UE and the UPF includes two parts: one part is QoS control for the connection between the remote UE and the UE-to-network relay, and the other part is QoS control for the connection between the UE-to-network relay and the UPF. In this solution, the PCF is responsible for setting QoS parameters between the UE and the UE-to-network relay (we refer to it as "PC5 QoS parameters") and between the UE-to-network relay and the UPF (we refer to it as "Uu QoS parameters") separately to support QoS requirements between the remote UE and the UPF.

For the PC5 interface, when standardized PQI is used, the PC5 QoS parameters include PQI and other optional QoS parameters, such as GFBR. When non-standardized PQI is used, a complete set of PC5 QoS characteristics is also included.

The PCF ensures that the PDB associated with 5QI in Uu QoS parameters and the PDB associated with PQI in PC5 QoS parameters support PDBs between remote UE and UPF. The PCF also ensures that other QoS parameters/QoS characteristics in Uu QoS parameters, e.g., PC5 QoS parameters, are compatible, e.g., have the same value.

The UE-to-network relay and remote UE are preconfigured with authorized services and associated PC5 QoS parameters. These may be provided by the PCF during the provisioning procedure. The PCF may also provide default PC5 QoS parameters to NW relay and remote UEs, which may be used for remote UEs that are out of coverage or for applications that are not frequently used.

When the remote UE wants to use the service provided by the AF over the 3GPP network, it selects the UE-to-network relay and establishes a PC5 connection between the remote UE and NW relay, if the remote UE does not have a PC5 QoS parameter for the service, then the default PC5 QoS flow is set using the default PC5 QoS parameter in the provisioning information.

The UE-to-network relay also sets up the corresponding PDU session for relaying the DNN requested by the remote UE, e.g., based on S-nsai. After the IP address/prefix assignment, the UE-to-network relay reports the remote UE's IP information to the SMF, from which the PCF also receives the remote UE's IP information.

If the remote UE does not have the PC5 QoS parameters for the service, after the PC5 connection and associated PDU session setup, the remote UE interacts with the AF to get the application layer control messages required for the service, which interaction is conveyed by the default PC5 QoS flow and default QoS flow of the PDU session. The AF then provides the service requirements to the PCF. Since the PCF has received the remote UE report from the SMF, the PCF knows that the target UE requested by the AF is a remote UE, the PCF generates PCC rules (for QoS control on Uu) and PC5 QoS parameters (for QoS control on PC 5), and the PCF decision may be based on, for example, service requirements and operator policies received from the AF and tariffs for Uu and PC 5.

Alternatively, the remote UE may send the E2E QoS requirements to the PCF via the relay UE by PC5 and NAS messages without involving AF, and then the PCF performs E2E QoS partitioning and generates PCC rules and PC5 QoS parameters based on the E2E QoS requirements provided by the remote UE.

6.25.2 programs related to AF

Fig. 6.25.2-1 entitled "QoS control for L3 UE-to-network relay involving AF" of [3GPP TR 23.752 V0.5.0 is reproduced as fig. 27]

1. When the remote UE wants to use the service provided by the AF over the 3GPP network, it selects the UE-to-network relay and establishes a PC5 connection between the remote UE and NW relay, which is the same as part of PC5 of step 3 described in clause 6.6.2. In this step, if the remote UE does not have a PC5 QoS parameter for the service, the default PC5 QoS flow is set using the default PC5 QoS parameter in the provisioning information.

The UE-to-network relay establishes a corresponding PDU session or uses an existing PDU session for relaying DNNs requested by the remote UE, e.g., based on S-nsai.

3. After IP address/prefix assignment, the UE-to-network relay reports the remote UE's IP information to the SMF, which also forwards the received report to the PCF.

4. If the remote UE does not have PC5 QoS parameters for the service, the remote UE interacts with the AF for application layer control messages required for the service, the interactions being communicated over the default PC5 QoS flows and default QoS flows of the PDU session.

5. Since the address used by the remote UE belongs to the PDU session of the UE-to-network relay, the AF is able to locate the PCF of the UE-to-network relay and provide service requirements to the PCF.

The pcf knows that the target UE requested by the AF is a remote UE, for example by IP information provided by the AF and IP information of the remote UE received from the SMF. The PCF generates PCC rules (for QoS control on Uu) and PC5 QoS parameters (for QoS control on PC 5), and the PCF decision may be based on, for example, service requirements and operator policies received from the AF and tariffs for Uu and PC 5. The PCF provides PCC decisions to the SMF.

7. Based on the PCC rules received from the PCF, the SMF may decide to set up a new QoS flow or modify an existing QoS flow for the PDU session. The SMF generates QoS rules to be enforced at the UE-to-network relay and QoS profiles to be enforced at the RAN for QoS control of the Uu part. A PDU session modification procedure is performed. The PC5 QoS parameters are also provided to the UE-to-network relay along with the associated QoS rules.

Ue to network relay initiates a layer 2 link modification procedure as described in TS 23.287[5] using PC5 QoS parameters received from the CN.

Note that: in the case of using the network scheduling operation mode for NR PC5, the procedure defined in TS 23.287[5] clause 5.4.1.4 is used to authorize the PC5 QoS request related to the relay operation.

The editor annotates: how to determine the PC5 QoS parameters and QoS parameters for a PDU session is to be further investigated, e.g. which UE subscription to use.

6.25.3 procedures not involving AF

Fig. 6.25.3-1 entitled "QoS control for L3 UE-to-network relay not involving AF" of [3GPP TR 23.752 V0.5.0 is reproduced as fig. 28]

1-3. Steps 1-3 are the same as steps 1-3 of clause 6.25.2.

4. The remote UE sends the E2E QoS requirement information to the UE-to-network relay. The E2E QoS requirement information may be an application requirement (e.g., priority requirement, reliability requirement, delay requirement) or an E2E QoS parameter. The E2E QoS parameters may be derived from application requirements or based on a mapping of ProSe service types to E2E QoS parameters.

Note that: similar to V2X communications, authorization and provisioning for ProSe communications is contemplated containing mapping of ProSe service types to E2E QoS parameters.

UE-to-network relay forwards E2E QoS requirement information to the SMF via a remote UE report with remote UE information.

The SMF also forwards the E2E QoS requirement information to the SMF through the SM policy association modification procedure.

PCF decides PCC rules and PC5 QoS parameters based on E2E QoS requirement information, operator policy, and tariffs for Uu and PC 5. The PCF provides PCC rules and PC5 QoS parameters to the SMF.

8-9. The treatments of steps 8-9 are the same as steps 7-8 of clause 6.25.2.

6.25.4 impact on services, entities and interfaces

PCF：

The PCF generates PCC rules (for QoS control on Uu) and PC5 QoS parameters (for QoS control on PC 5).

SMF：

-providing PC5 QoS parameters to the UE-to-network relay during the PDU session modification procedure.

UE to network relay:

UE-to-network relay modifies the layer 2 link based on the PC5 QoS parameters received from the CN.

-forwarding E2E QoS requirements received from the remote UE to the CN.

Remote UE:

-sending the E2E QoS requirements to the UE-to-network relay.

According to 3gpp TR 23.752, UE-to-network relay communications are investigated for UEs accessing a network via indirect network communications. Basically, a Rel-16 5g architecture design (e.g., flow-based QoS communication over the PC5/Uu interface) can be considered. In the context of UE-to-network relay communications, a remote UE will access the network (e.g., 5 GC) via a relay UE, where the remote UE will be out of coverage and the relay UE will be in coverage. The remote UE will communicate with the relay UE via a PC5 interface (or referred to as a side link interface) for accessing the network, while the relay UE will communicate with the base station (e.g., the gNB) via a Uu interface for forwarding traffic between the remote UE and the network.

The remote UE may be able to reuse the procedures described in 3gpp TS 23.287 and TS 24.587 (e.g., PC5 unicast link setup procedure, PC5 unicast link authentication procedure, PC5 unicast link security mode control procedure and/or the like) to establish a direct link with the relay UE. In the PC5 unicast link setup procedure, the first UE may send a first PC5-S message (e.g., a direct link setup request or a direct communication request) to the second UE for requesting establishment of a unicast link with the second UE. In response to receiving the first PC5-S message, the second UE may send a second PC5-S message (e.g., a direct link security mode command or a security mode command) to the first UE for establishing a security context (including, for example, PEK, PIK, and/or a security algorithm) between the two UEs.

After receiving the second PC5-S message, the first UE may send a third PC5-S message (e.g., direct link security mode complete or security mode complete) to the second UE for completing the security context setup. And then the second UE may send a fourth PC5-S message (e.g., a direct link setup accept or a direct communication accept) to the first UE for completing the unicast link setup. For security, the PC5QoS information of the unicast link should be protected. The PC5 quality of service (QoS) information may indicate one or more PC5QoS flows for the unicast link. Each PC5QoS flow may be associated with a PC5 flow ID (PFI) and a corresponding PC5QoS parameter (i.e., PC5 5QI (PQI) and conditionally other parameters such as Maximum Flow Bit Rate (MFBR)/Guaranteed Flow Bit Rate (GFBR), etc.). Thus, the PC5QoS information (requested by the first UE) may be included in the third PC5-S message, as the third PC5-S message is sent with protection (using, for example, PEK, PIK and/or security algorithms). And, the PC5QoS information (accepted by the second UE) may be included in the fourth PC5-S message because the fourth PC5-S message is sent with protection. In order for the remote UE to perform UE-to-network relay communications with the relay UE, the remote UE may reuse such a PC5 unicast link setup procedure to establish a direct link with the relay UE. In other words, the remote UE may correspond to a first UE and the relay UE may correspond to a second UE, or vice versa.

According to 3gpp TR 23.752, for a remote UE to access a network via a relay UE, qoS control between the remote UE and a User Plane Function (UPF) comprises two parts: one part is QoS control for a connection between a remote UE and a relay UE, and the other part is QoS control for a connection between a relay UE and a UPF. The Policy Control Function (PCF) may be responsible for setting QoS parameters between the remote UE and the relay UE (so-called "PC5QoS parameters") and between the relay UE and the UPF (so-called "Uu QoS parameters") separately to support the (end-to-end) QoS requirements between the remote UE and the UPF.

If the remote UE does not have PC5QoS parameters for the service (using UE-to-network relay communications), the remote UE may interact with an Application Function (AF) to get the application layer control messages needed for the service. The PCF may then know that the target UE requested by the AF is a remote UE and generate Policy and Charging Control (PCC) rules (for QoS control on Uu) and PC5QoS parameters (for QoS control on PC 5). The PCF decisions may be based on service requirements received from the AF. The PCF may provide the PCC decision to the SMF. Based on the PCC rules received from the PCF, a Session Management Function (SMF) may decide to set up a new QoS flow or modify an existing QoS flow for a Protocol Data Unit (PDU) session of the service. The SMF may generate QoS rules to be enforced at the relay UE and QoS profiles to be enforced at the RAN (radio access network, e.g. base station or gNB) for QoS control of the Uu part. Thus, the SMF may perform a PDU session modification procedure for QoS control on Uu and/or provide PC5QoS parameters to the relay UE along with related QoS rules.

And then the relay UE may perform, for example, a layer 2 link modification procedure with the remote UE for the PC5 QoS parameters. In other words, the PC5 QoS information does not have to be negotiated in the procedure of direct link establishment, since the network will determine the PC5 QoS parameters for UE-to-network relay communication anyway, and then the relay UE and the remote UE will apply the PC5 QoS parameters determined by the network after the procedure of direct link establishment is completed. Thus, PC5 QoS information negotiated in the procedure of direct link setup will cause signaling overhead.

To address the problem, the remote UE (and/or relay UE) may not need to negotiate PC5 QoS information within the procedure of establishing a direct link between the relay UE and the remote UE. More specifically, the presence of PC5 QoS information may be optional in any PC5-S messages exchanged between the remote UE and the relay UE within the procedure of establishing a direct link between the remote UE and the relay UE. This concept can be applied in PC5-S messages for accomplishing security context establishment within the program that establishes the direct link. In this example, this PC5-S message may be, for example, a direct link security mode complete or a security mode complete message. This concept can (also) be applied in PC5-S messages for completing the procedure of establishing a direct link. In this example, this PC5-S message may be, for example, a direct link setup accept or a direct communication accept message.

In the above example, if this PC5-S message is sent within the procedure of establishing a direct link between the remote UE and the relay UE, then PC5QoS information may not be present in this PC5-S message. If this PC5-S message is sent in-process of establishing a unicast link between two UEs (i.e., not used for UE-to-network relay communications), then PC5QoS information may be present in this PC5-S message.

In the case of inter-UE relay communication (i.e., UE1 and UE2 communicate with each other via a relay UE), the above concepts will not apply because no network instance will be responsible for determining the PC5QoS parameters for the PDU session established between UE1 and UE 2. In practice, the PC5QoS parameters for the first direct link between UE1 and the relay UE may be negotiated between UE1 and the relay UE within the procedure of establishing the first direct link. Similarly, PC5QoS parameters for a second direct link between relay UE and UE2 may be negotiated between relay UE and UE2 within the procedure of establishing the second direct link.

Fig. 29 is a flow chart 2900 of establishing a one-to-one connection between a first UE and a second UE from the perspective of the second UE according to an example embodiment. In step 2905, the second UE initiates a first procedure to establish a one-to-one connection with the first UE for unicast communication between the first UE and the second UE or for inter-UE communication between the first UE and a third UE via the second UE, or a second procedure to establish a one-to-one connection with the first UE for UE-to-network communication between the first UE and a network node via the second UE. In step 2910, the second UE transmits a first PC5-S message to the first UE for completing a first procedure to establish a one-to-one connection with the first UE for unicast communication or inter-UE communication with the first procedure initiated, wherein the first PC5-S message includes quality of service (QoS) information for unicast communication or inter-UE communication. In step 2915, the second UE transmits a second PC5-S message to the first UE for completing a second procedure to establish a one-to-one connection with the first UE for UE-to-network communication with the second procedure initiated, wherein the second PC5-S message does not contain any QoS information for UE-to-network communication.

In one embodiment, the second UE may receive a third PC5-S message from the first UE for initiating a first procedure to establish a one-to-one connection or a second procedure to establish a one-to-one connection. The third PC5-S message may be a direct communication request message or a direct link establishment request message, and the first or second PC5-S message may be a direct communication accept message or a direct link establishment accept message.

In one embodiment, the second UE may transmit a fourth PC5-S message to the first UE for establishing a first security context for the one-to-one connection in a first procedure for establishing the one-to-one connection or for establishing a second security context for the one-to-one connection in a second procedure for establishing the one-to-one connection. The second UE may also receive a fifth PC5-S message from the first UE for completing the establishment of the first security context in a first procedure for establishing a one-to-one connection or for completing the establishment of the second security context in a second procedure for establishing a one-to-one connection. The fourth PC5-S message may be a secure mode command message or a direct link secure mode command message, and wherein the fifth PC5-S message is a secure mode complete message or a direct link secure mode complete message.

In one embodiment, the presence of QoS information in the first or second PC5-S message may be defined as optional. Alternatively, the presence of QoS information in the first PC5-S message may be defined as mandatory. In addition, qoS information may not be defined in the second PC5-S message.

Referring back to fig. 3 and 4, in one exemplary embodiment of the second UE establishing a one-to-one connection between the first UE and the second UE. The second UE 300 includes program code 312 stored in memory 310. CPU 308 may execute program code 312 to enable the second UE to: (i) a first procedure to initiate a one-to-one connection with a first UE for unicast communication between the first UE and a second UE or for inter-UE communication between the first UE and a third UE via the second UE, or a second procedure to establish a one-to-one connection with the first UE for UE-to-network communication between the first UE and a network node via the second UE, (ii) a first procedure to transmit a first PC5-S message to the first UE for completing the one-to-one connection with the first UE for unicast communication or inter-UE communication if the first procedure is initiated, wherein the first PC5-S message includes QoS information for unicast communication or inter-UE communication, and (iii) a second procedure to transmit a second PC5-S message to the first UE for completing the one-to-one connection with the first UE for UE-to-network communication if the second procedure is initiated, wherein the second PC5-S message does not include any QoS information for UE-to-network communication. Further, the CPU 308 may execute the program code 312 to perform all of the above-described acts and steps or other acts and steps described herein.

Fig. 30 is a flowchart 3000 of establishing a one-to-one connection between a first UE and a second UE, from the perspective of the second UE, according to an example embodiment. In step 3005, the second UE receives a first PC5-S message from the first UE for initiating a procedure to establish a one-to-one connection. In step 3010, the second UE transmits a second PC5-S message to the first UE for establishing a security context between the first UE and the second UE in the procedure of establishing the one-to-one connection. In step 3015, the second UE receives a third PC5-S message from the first UE for completing the establishment of the security context in the procedure for establishing the one-to-one connection. In step 3020, the second UE transmits a fourth PC5-S message to the first UE for completing the procedure of establishing the one-to-one connection, wherein the presence of quality of service (QoS) information in the fourth PC5-S message is defined as optional.

In one embodiment, the fourth PC5-S message may include QoS information if the one-to-one connection is used for unicast communication between the first UE and the second UE or inter-UE communication between the first UE and the third UE via the second UE, and the fourth PC5-S message does not include any QoS information if the one-to-one connection is used for UE-to-network communication between the first UE and the network node via the second UE. Further, the first PC5-S message may be a direct communication request message or a direct link establishment request message, and the fourth PC5-S message may be a direct communication acceptance message or a direct link establishment acceptance message. In addition, the second PC5-S message may be a secure mode command message or a direct link secure mode command message, and the third PC5-S message may be a secure mode complete message or a direct link secure mode complete message.

Referring back to fig. 3 and 4, in one exemplary embodiment of the second UE establishing a one-to-one connection between the first UE and the second UE. The second UE 300 includes program code 312 stored in memory 310. CPU 308 may execute program code 312 to enable the second UE to: (i) receiving a first PC5-S message from the first UE for initiating a procedure for establishing a one-to-one connection, (ii) transmitting a second PC5-S message to the first UE for establishing a security context between the first UE and the second UE in the procedure for establishing a one-to-one connection, (iii) receiving a third PC5-S message from the first UE for completing the establishment of the security context in the procedure for establishing a one-to-one connection, and (iv) transmitting a fourth PC5-S message to the first UE for completing the procedure for establishing a one-to-one connection, wherein the presence of QoS information in the fourth PC5-S message is defined as optional. Further, the CPU 308 may execute the program code 312 to perform all of the above-described acts and steps or other acts and steps described herein.

Fig. 31 is a flowchart 3100 of performing a procedure for establishing a one-to-one connection between a first UE and a second UE according to an example embodiment from the perspective of the second UE. In step 3105, the second UE receives a third PC5-S message from the first UE within the procedure for establishing the one-to-one connection, wherein the presence of QoS information in the third PC5-S message is optional.

In one embodiment, the second UE may receive a first PC5-S message from the first UE for initiating a procedure for establishing a one-to-one connection. The second UE may also transmit a second PC5-S message to the first UE for establishing a security context between the first UE and the second UE within the procedure for establishing the one-to-one connection. The third PC5-S message may be used to complete a security context setup between the first UE and the second UE.

In one embodiment, the second UE may transmit a fourth PC5-S message to the first UE for completing the procedure of establishing the one-to-one connection, wherein the presence of QoS information in the fourth PC5-S message is optional. The second PC5-S message may be transmitted to the first UE in response to receiving the first PC5-S message from the first UE. The fourth PC5-S message may be transmitted to the first UE in response to receiving the third PC5-S message from the first UE.

In one embodiment, the third PC5-S message may contain the first QoS information if the one-to-one connection is used for unicast communication or inter-UE relay communication. The third PC5-S message may not contain any QoS information if the one-to-one connection is used for UE-to-network relay communication.

In one embodiment, the fourth PC5-S message may contain second QoS information if the one-to-one connection is for unicast communication or inter-UE relay communication. The fourth PC5-S message may not include any QoS information if the one-to-one connection is used for UE-to-network relay communication.

In one embodiment, if the one-to-one connection is for UE-to-network relay communications or inter-UE relay communications, the first UE may be a remote UE and the second UE may be a relay UE.

Referring back to fig. 3 and 4, in one exemplary embodiment of the second UE performing a procedure for establishing a one-to-one connection between the first UE and the second UE. The second UE 300 includes program code 312 stored in memory 310. CPU 308 may execute program code 312 to enable the second UE to receive a third PC5-S message from the first UE within the procedure for establishing a one-to-one connection, wherein the presence of QoS information in the third PC5-S message is optional. Further, the CPU 308 may execute the program code 312 to perform all of the above-described acts and steps or other acts and steps described herein.

Various aspects of the invention have been described above. It should be understood that the teachings herein may be embodied in a wide variety of forms and that any specific structure, function, or both being disclosed herein is merely representative. Based on the teachings herein one skilled in the art should appreciate that an aspect disclosed herein may be implemented independently of any other aspects and that two or more of these aspects may be combined in various ways. For example, an apparatus may be implemented or a method practiced using any number of the aspects set forth herein. In addition, such apparatus may be implemented or such method may be practiced using other structure, functionality, or structure and functionality in addition to or other than one or more of the aspects set forth herein. As an example of some of the above concepts, in some aspects, parallel channels may be established based on pulse repetition frequencies. In some aspects, parallel channels may be established based on pulse positions or offsets. In some aspects, parallel channels may be established based on a hopping sequence. In some aspects, parallel channels may be established based on pulse repetition frequency, pulse position, or offset, and time hopping sequences.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, processors, means, circuits, and algorithm steps described in connection with the aspects disclosed herein may be implemented as electronic hardware (e.g., digital implementations, analog implementations, or combinations of both, which may be designed using source coding or some other technique), various forms of program or design code incorporating instructions (which may be referred to herein as "software" or a "software module" for convenience), or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

Additionally, the various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented within or performed by an integrated circuit ("IC"), an access terminal, or an access point. An IC may comprise a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, electrical components, optical components, mechanical components, or any combination thereof designed to perform the functions described herein, and may execute code or instructions that reside within the IC, outside the IC, or both. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

It should be understood that any particular order or hierarchy of steps in any disclosed process is an example of an example approach. It should be understood that the specific order or hierarchy of steps in the process may be rearranged based on design preferences while remaining within the scope of the present disclosure. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

The steps of a method or algorithm described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. Software modules (e.g., containing executable instructions and associated data) and other data may reside in data storage such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of computer-readable storage medium known in the art. An example storage medium may be coupled to a machine, such as a computer/processor (which may be referred to herein as a "processor" for convenience), such that the processor can read information (e.g., code) from, and write information to, the storage medium. An example storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user equipment. In the alternative, the processor and the storage medium may reside as discrete components in a user device. Furthermore, in some aspects, any suitable computer program product may comprise a computer-readable medium comprising code relating to one or more of the aspects of the present disclosure. In some aspects, the computer program product may include packaging material.

While the invention has been described in connection with various aspects, it will be understood that the invention is capable of further modifications. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known and customary practice within the art to which the invention pertains.

Claims

1. A method for a second user device to establish a one-to-one connection between a first user device and the second user device, comprising:

initiating a procedure to establish the one-to-one connection with the first user device, wherein the procedure is to support (i) unicast communications between the first user device and the second user device, and (ii) user device-to-network communications between the first user device and a network node via the second user device;

transmitting a first PC5-S message to the first user equipment for completing the one-to-one connection with the first user equipment upon initiating the procedure for the unicast communication, wherein a field of quality of service information in the first PC5-S message is quality of service information present for indicating the unicast communication; and

When the procedure is initiated for the user device to network communication, a second PC5-S message is transmitted to the first user device for completing the one-to-one connection with the first user device, wherein a field of the quality of service information in the second PC5-S message is absent to not indicate any quality of service information for the user device to network communication.

2. The method as recited in claim 1, further comprising:

a third PC5-S message is received from the first user equipment for initiating the procedure for establishing the one-to-one connection.

3. The method of claim 2, wherein the third PC5-S message is a direct communication request message or a direct link establishment request message, and the first or second PC5-S message is a direct communication accept message or a direct link establishment accept message.

4. The method as recited in claim 1, further comprising:

transmitting a fourth PC5-S message to the first user equipment for establishing a first security context for the one-to-one connection in the procedure for establishing the one-to-one connection or for establishing a second security context for the one-to-one connection in the procedure for establishing the one-to-one connection; and

A fifth PC5-S message is received from the first user equipment for completing the establishment of the first security context in the procedure for establishing the one-to-one connection or for completing the establishment of the second security context in the procedure for establishing the one-to-one connection.

5. The method of claim 4, wherein the fourth PC5-S message is a secure mode command message or a direct link secure mode command message, and wherein the fifth PC5-S message is a secure mode complete message or a direct link secure mode complete message.

6. A method for a second user device to establish a one-to-one connection between a first user device and the second user device, comprising:

receiving a first PC5-S message from the first user equipment for initiating a procedure for establishing the one-to-one connection;

transmitting a second PC5-S message to the first user equipment for establishing a security context between the first user equipment and the second user equipment in the procedure for establishing the one-to-one connection;

receiving a third PC5-S message from the first user equipment for completing the establishment of the security context in the procedure for establishing the one-to-one connection; and

Transmitting a fourth PC5-S message to the first user equipment for completing the procedure of establishing the one-to-one connection, wherein the presence of quality of service information in the fourth PC5-S message is defined as optional;

wherein the fourth PC5-S message includes quality of service information if the one-to-one connection is used for unicast communication between the first user equipment and the second user equipment or inter-user equipment communication between the first user equipment and a third user equipment, and the fourth PC5-S message does not include any quality of service information if the one-to-one connection is used for user equipment to network communication between the first user equipment and a network node, via the second user equipment.

7. The method of claim 6, wherein the first PC5-S message is a direct communication request message or a direct link establishment request message, and the fourth PC5-S message is a direct communication accept message or a direct link establishment accept message.

8. The method of claim 6, wherein the second PC5-S message is a secure mode command message or a direct link secure mode command message and the third PC5-S message is a secure mode complete message or a direct link secure mode complete message.

9. A second user device, comprising:

a control circuit;

a processor mounted in the control circuit; and

a memory mounted in the control circuit and operatively coupled to the processor;

wherein the processor is configured to execute program code stored in the memory to:

initiating a procedure to establish a one-to-one connection with a first user equipment, wherein the procedure is to support (i) unicast communication between the first user equipment and the second user equipment, and (ii) user equipment-to-network communication between the first user equipment and a network node via the second user equipment; and

10. The second user device of claim 9, wherein the processor is further configured to execute program code stored in the memory to:

11. The second user equipment according to claim 10, wherein the third PC5-S message is a direct communication request message or a direct link establishment request message, and the first or second PC5-S message is a direct communication accept message or a direct link establishment accept message.

12. The second user device of claim 9, wherein the processor is further configured to execute program code stored in the memory to:

13. The second user device of claim 12, wherein the fourth PC5-S message is a secure mode command message or a direct link secure mode command message, and wherein the fifth PC5-S message is a secure mode complete message or a direct link secure mode complete message.